Make sure that ctrl-c works properly with GHC 7.8.* and QuickCheck-2.6

The `interrupted` flag does not work with GHC 7.8.* (see
https://github.com/nick8325/quickcheck/commit/57bfa874b3d9733afd32da98f83cadfa2d9fffed).
This is why we now rely on string comparison instead (the way we already
do it for QuickCheck < 2.6).
Use enclosed-exceptions to implement safeTry

I haven't been able to get a reliable reproducing case yet, but we had
some code where some failing test cases ended up bringing down the
entire test process. I can't be 100% that this solves the problem, but
I've run the test suite multiple times with this change, and everything
seems correct.

This seems to have come from the fact that we're using the async
library, and the race function in particular, to have multiple
concurrent actions running in our tests. (I can provide more details if
relevant.) async was using AsyncException to kill threads, which was
somehow propagating too far.
Add missing evaluate (see #171)
Fix tests (see #171)
Do not depend on enclosed-exceptions (see #171)
Remove redundant code
Minor refactoring
Update CHANGES
Remove `Example` instance for `Test.HUnit.Test` (#101)
Remove deprecated functions
Update CHANGES
Do not reexport `property` from `Test.Hspec.QuickCheck`
Move requirement text from Item to SpecItem constructor
Move ProgressCallback out of Params
Update CHANGES
Bump version
Rename hspec.cabal -> hspec-meta.cabal
Remove cabal test-suite sections
Rename package to hspec-meta
Adapt synopsis and description