Add special __dict__ attribute to extension types

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