Replace Tokyo use with Ceygen and unbundle it

End of BLAS/LAPACK mess, yay!
Transition PyBayes to use Cython memoryviews instead of NumPy arrays

TODO: work with Cython 0.18 without custom patches
Port stress testing to unittest, happens in build directory now
setup.py: consistency with Ceygen, read long desc from README
pdfs: prevent vectors with 0 elements

...Cython arrays don't like it.
filters: prevent matrices with 0 elements

...Cython arrays don't like it.
Add initial .travis.yml to try building on Travis CI
Tweak .travis.yml
travis.yml: install Eigen for Ceygen
README.rst: mention Ceygen dependency version
stress_filters: skip Kalman stress unless SciPy is found

Also add compatibility skip, skipIf, skipUnless decorators to test support.
Let's not strive for Py 2.6 compatibility
support: Py 3 compatibility
Fix stress_filters
Python 3 compatibility
Definitive Python 3 compatibility
support/stress and test commands: pass verbosity argument to tests
dist_cmd_test: drop support for making the command non-fatal
ChangeLog: add notes about Cython memoryview transition
doc/conf.py: make documentation build-able again