Merge pull request #7 from hvr/master

Add Travis-CI script
Rename and document inlinePerformIO to better reflect its behaviour

We've had a few instances of people being tempted to use it without
really understanding the consequences.
Fixed logic on CONLIKE hack.

Based closely on a patch by Stijn van Drongelen <rhymoid@gmail.com>
QuickCheck update from yesterday breaks the build

QuickCheck 2.7 changed `Property` to a newtype instead of a type synonym. This should fix it until we update our test code.
Make travis builds work again

QuickCheck 2.7 broke it, so we need a tighter upper bound (already fixed in the .cabal file)
Updated README
Whoops, the .cabal file referred to the README
Delete prologue.txt

No need for this anymore
Update .travis.yml description

Note: this drops GHC 6.12 and a few interim GHC releases from the GHC matrix