Check exception is thrown if without ahmed in some tests

These tests used to fail when BEM is compiled without AHMED.
Now the tests explcitly check that an exception is thrown warning  that the code is compiled without
ahmed.
Update code to use numpy.i for numpy 1.8

Unfortunately, the function `require_fortran` in numpy.i does not follow the convention from the
other `require_*` defined there.
We add a `expect_fortran` function that does, and use it in armadillo2numpy.i. All python unit tests
pass.
Adding python+tests to the build system

Both c++ and python unit tests can be run through the ctest framework.
Closes issue #71.
Add labels for c++ unit tests
Adds input sanity check in debug mode

Some checks are disabled when  compiling with NDEBUG. They are reinstated within the python
framework by adding a "check" typemap.
Closes #79