Improve documentation for cpdef methods

Use automatic PEP links in doc

Allow C++ class methods to use base class' methods

Add tp_dict and tp_descr_* declarations

let's see if the list order of the python releases makes a difference for the execution order in travis

extract some changes from pull request #504 that seem straight forward and helpful to speed up the travis builds

Update docs wrt property syntax deprecation

Allow passing define macros without specified values as commented directives

Add no_gc directive to fully disable GC

follow PEP492 change in Py3.5.2 that makes __aiter__() a simple function instead of an async function
See https://bugs.python.org/issue27243

numpy arrays are no longer omitted from locals()

Improve "missing cimport" message