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
Remove doctest dependency

(so that we can use haddock-library with doctest)
Travis tweaks
Don't actually forget to install specified GHC.
Removed reliance on LambdaCase (which breaks build with ghc 7.4).
Fixed haddock warnings.
Update Travis, bump version
Fix anchors. Closes #308.
Drop DocParagraph from front of headers

I can not remember why they were wrapped in paragraphs to begin with and
it seems unnecessary now that I test it. Closes #307.
Don't mangle append order for nested lists.

The benefit of this is that the ‘top-level’ element of such lists is
properly wrapped in <p> tags so any CSS working with these will be
applied properly. It also just makes more sense.

Pointed out at jgm/pandoc#1346.
Bump haddock-library to 1.1.0 for release
Propagate overloading-mode for instance declarations in haddock (#9242)
Adapt to new definition of HsDecls.TyFamEqn

This is a knock-on from the refactoring from Trac #9063.
I'll push the corresponding changes to GHC shortly.
Track GHC PackageId to PackageKey renaming.

Signed-off-by: Edward Z. Yang <ezyang@cs.stanford.edu>

Conflicts:
	src/Haddock/Interface/Create.hs
Track changes for module reexports.

Signed-off-by: Edward Z. Yang <ezyang@cs.stanford.edu>

Conflicts:
	src/Haddock/Interface/Create.hs
Catch mid-line URLs. Fixes #314.
Track type signature change of lookupModuleInAllPackages

Signed-off-by: Edward Z. Yang <ezyang@cs.stanford.edu>
If GhcProfiled, also build Haddock profiled.

Signed-off-by: Edward Z. Yang <ezyang@cs.stanford.edu>