Add MM/YYYY and MM/YY

Summary:
MM/YY is a common format for dates in India,UK and other parts of the world.Have added testcases in `Time/EN/corpus.hs` ,however it conflicts with one of the original(2/15 is output now as Feb. 2015 and not the 15th of February).
Closes https://github.com/facebookincubator/duckling/pull/59

Reviewed By: niteria

Differential Revision: D5455881

Pulled By: patapizza

fbshipit-source-id: 23b73a5

Duckling/Ranking/Classifiers/EN.hs

@@ -59,12 +59,12 @@ classifiers
                                likelihoods = HashMap.fromList [], n = 0}}),
        ("integer (numeric)",
         Classifier{okData =
-                     ClassData{prior = -0.8594418676420025,
+                     ClassData{prior = -0.8649974374866046,
                                unseen = -5.0369526024136295,
                                likelihoods = HashMap.fromList [("", 0.0)], n = 152},
                    koData =
-                     ClassData{prior = -0.5506035952229099, unseen = -5.342334251964811,
-                               likelihoods = HashMap.fromList [("", 0.0)], n = 207}}),
+                     ClassData{prior = -0.5465437063680699, unseen = -5.351858133476067,
+                               likelihoods = HashMap.fromList [("", 0.0)], n = 209}}),
        ("<duration> hence|ago",
         Classifier{okData =
                      ClassData{prior = 0.0, unseen = -3.784189633918261,
@@ -137,6 +137,15 @@ classifiers
                    koData =
                      ClassData{prior = -infinity, unseen = -0.6931471805599453,
                                likelihoods = HashMap.fromList [], n = 0}}),
+       ("mm/yyyy",
+        Classifier{okData =
+                     ClassData{prior = -0.6931471805599453,
+                               unseen = -1.0986122886681098,
+                               likelihoods = HashMap.fromList [("", 0.0)], n = 1},
+                   koData =
+                     ClassData{prior = -0.6931471805599453,
+                               unseen = -1.0986122886681098,
+                               likelihoods = HashMap.fromList [("", 0.0)], n = 1}}),
        ("integer after|past <hour-of-day>",
         Classifier{okData =
                      ClassData{prior = 0.0, unseen = -2.3025850929940455,
@@ -1245,8 +1254,8 @@ classifiers
                      ClassData{prior = -infinity, unseen = -0.6931471805599453,
                                likelihoods = HashMap.fromList [], n = 0},
                    koData =
-                     ClassData{prior = 0.0, unseen = -2.890371757896165,
-                               likelihoods = HashMap.fromList [("", 0.0)], n = 16}}),
+                     ClassData{prior = 0.0, unseen = -2.9444389791664407,
+                               likelihoods = HashMap.fromList [("", 0.0)], n = 17}}),
        ("Sunday",
         Classifier{okData =
                      ClassData{prior = 0.0, unseen = -2.3025850929940455,
@@ -1300,15 +1309,15 @@ classifiers
                                n = 40}}),
        ("year",
         Classifier{okData =
-                     ClassData{prior = -0.21622310846963594,
+                     ClassData{prior = -0.24362208265775043,
                                unseen = -3.4339872044851463,
                                likelihoods = HashMap.fromList [("integer (numeric)", 0.0)],
                                n = 29},
                    koData =
-                     ClassData{prior = -1.6376087894007967,
-                               unseen = -2.1972245773362196,
+                     ClassData{prior = -1.5314763709643884,
+                               unseen = -2.3025850929940455,
                                likelihoods = HashMap.fromList [("integer (numeric)", 0.0)],
-                               n = 7}}),
+                               n = 8}}),
        ("last <day-of-week> of <time>",
         Classifier{okData =
                      ClassData{prior = 0.0, unseen = -2.3978952727983707,

Duckling/Time/EN/Corpus.hs

@@ -56,6 +56,9 @@ allExamples = concat
              [ "today"
              , "at this time"
              ]
+  , examples (datetime (2013, 2, 1, 0, 0, 0) Day)
+             [ "2/2013"
+             ]
   , examples (datetime (2013, 2, 11, 0, 0, 0) Day)
              ["yesterday"]
   , examples (datetime (2013, 2, 13, 0, 0, 0) Day)

Duckling/Time/EN/Rules.hs

@@ -683,6 +683,20 @@ ruleHalfHOD = Rule
       _ -> Nothing
   }
 
+ruleMMYYYY :: Rule
+ruleMMYYYY = Rule
+  { name = "mm/yyyy"
+  , pattern =
+    [ regex "(0?[1-9]|1[0-2])[/-](\\d{4})"
+    ]
+  , prod = \tokens -> case tokens of
+      (Token RegexMatch (GroupMatch (mm:yy:_)):_) -> do
+        y <- parseInt yy
+        m <- parseInt mm
+        tt $ yearMonthDay y m 1
+      _ -> Nothing
+  }
+
 ruleMMDDYYYY :: Rule
 ruleMMDDYYYY = Rule
   { name = "mm/dd/yyyy"
@@ -1608,6 +1622,7 @@ rules =
   , ruleMMDDYYYY
   , ruleYYYYMMDD
   , ruleMMDD
+  , ruleMMYYYY
   , ruleNoonMidnightEOD
   , rulePartOfDays
   , ruleEarlyMorning