Haskell makefile won't try to build the doc by default.

Before, make would fail if you didn't have latex installed.
This change also include a new test suite for unit tests.
Small change to the haskell generated test programm:

When parsing fails, the program exits with a non-zero code.
Updated the travis settings

Now that there is some haskell tests, we can go back to using the
default build script.