Compatibility with older versions of base and bytestring
Enable travis-ci for haddock-library
haddock-library: Do not depend on haddock-library in test suite

I think you either add src to hs-source-dirs or the library to
build-depends.  But doing both does not make sense (AFAICT).
haddock-library: Use -Wall for specs
Use Travis with multiple GHC versions

When using HEAD, we build haddock-library directly from repository as a
dependency (and thanks to --enable-tests, the tests get ran anyway). In
all other cases, we manually run the tests on haddock-library only and
don't test the main project.
Comment improvements + few words in cabal file
Use doctest to check examples in documentation