Add strict variants of MutVar modification functions.
Bump primitive cabal version to 0.5.2.0
Add Travis-CI script
Add build-status icon and Hackage-link to README
Drop redundant FFI language extension pragma

...since `ForeignFunctionInterface` is implied by Haskell2010.

This also sets proper upper bounds on base and ghc-prim as this
`primitive` is too tightly coupled with those packages and very likely
to break with each major GHC release.
Turn on warnings for .c files
Fix compilation warning on OS X
Merge pull request #3 from iand675/master

Add strict variants of MutVar modification functions.
Update changelog