Merge pull request #29 from ghorn/llvm3.4

preliminary travis-ci integration
Allow llvm and clang to build PIC
Switch to chetant's Travis CI
Remove cruft and hard-coded paths from Setup.hs
Make 'cabal clean' clean LLVM
Derive more instances on enums
"rm -rf build/*" instead of "cd build; rm -rf *" to supress fresh cabal clean causing "/bin/sh: 1: cd: can't cd to build", updates 27429167adcf6d04daff590bf03b9f4b25ed0564