setup.py: Apps -> Apps.

[ci skip]
remove dependency for scipy and statsmodels
simplify requirements.txt
require numpy to be installed ahead of time

see, for example, http://numpy-discussion.10968.n7.nabble.com
/specifying-numpy-as-dependency-in-your-project-install-requires-
td32268.html
docs tweaks
travis.yml tweaks, removing scipy
installation docs
docs tweaks
add MANIFEST.in