Add benchmarks for hashmap package comparison
benchmarks: rename hashmap/HashMap to hashmap/Map
Merge branch 'master' of https://github.com/bgamari/unordered-containers
Make GHC >= 7.2 imports conditional
Remove support for compilers other than GHC

There are no other compilers.
Bump version number to 0.2.3.1
D.H.Strict: only evaluate values if used

Before this change all value arguments would be evaluated to WHNF even
if they were never inserted into the map. Fixes #69. Fixes #57.

Also fix a strictness bug in fromList (fixes #61).
Bump version number to 0.2.3.2
HashMap: Compatibility with GHC >= 7.7