Move extensions into src/extensions directory

spec/extensions/strip-trailing-whitespace-spec.coffee

@@ -1,4 +1,4 @@
-StripTrailingWhitespace = require 'extensions/strip-trailing-whitespace'
+StripTrailingWhitespace = require 'strip-trailing-whitespace'
 RootView = require 'root-view'
 fs = require 'fs'
 

src/extensions/command-interpreter.coffee

@@ -4,7 +4,7 @@ PEG = require 'pegjs'
 module.exports =
 class CommandInterpreter
   constructor: ->
-    @parser = PEG.buildParser(fs.read(require.resolve 'commands.pegjs'))
+    @parser = PEG.buildParser(fs.read(require.resolve 'command-interpreter/commands.pegjs'))
 
   eval: (editor, string) ->
     command = @parser.parse(string)

src/stdlib/require.coffee

@@ -3,6 +3,7 @@ paths = [
   "#{atom.loadPath}/benchmark"
   "#{atom.loadPath}/src/stdlib"
   "#{atom.loadPath}/src/app"
+  "#{atom.loadPath}/src/extensions"
   "#{atom.loadPath}/src"
   "#{atom.loadPath}/vendor"
   "#{atom.loadPath}/static"
@@ -128,4 +129,4 @@ this.require.nameToUrl = (path) -> "#{path}.js"
 this.require.__modules = __modules
 
 # issue #17
-this.require.noWorker = true
+this.require.noWorker = true