0.6.0 - Major API overhaul

Removed the Session monad, opening a direct access to the connection pool, thus providing for a simpler compatibility with other libraries.
The connection timeout is now set using Int for simplicity.
There are no exceptions any more. All the error-reporting is typed and done explicitly, using Either.
The error types are now mostly backend-specific.
The transaction mode is now extended to support uncommitable transactions with the TxWriteMode type.
Tx now has a MonadError instance, which allows to handle errors while remaining in the transaction.
All Tx functions now have a "Tx" suffix.
There is no more list transaction. Instead there is vectorTx.
The Statement type is renamed to Stmt and is now exported from the main API.
RowParser is now uninstantiable. This enforces the idiomatic usage of the library.

0.5.0