Make via cabal

[quchen]

Ditch the makefile for easier sandboxing, Travis integration etc.

• Separate library from executable (to get minimal dependencies for executables, avoid .cabal bloat)
• Update travis.yml (See also hackage-server's file for some inspiration)

Moved to #41 as separate refactorings:

• Add different build flavours to .cabal
• Delete Makefile, or at least reduce it to a minimum

[quchen]

Library/executable isolation done

[quchen]

Cabal builds work, travis.yml updated (but not tested)

[quchen]

Merged in 8fca27c51ba6e3d69f1e991a78020e0975880762

Travis works, makefile is still cabal-independent though. See #41 for the rest.