Create .travis.yml
Remove CPP hack and DoRec/RecursiveDo from L.hs

A CPP-based solution can't easily work here; L.hs is parsed by the eval
plugin during `@let`.  If DoRec/RecursiveDo (or any other
GHC-version-specific extensions) are to be supported properly, it will
require the eval plugin to translate the extension when updating the
module.  For now, recursive do is completely disabled.  I don't think
there has ever been a GHC that accepted both without whining.
Merge git://github.com/dagit/lambdabot