added repeat func to the cheatsheet

trigger rebuild

enabled index for site builds

Release/v0.7.3 (#230)

* version 0.7.3

* fixed GNG storage problem, added exceptions to GNG graph for safety,
added repr for GNG

* aded GNG node repr and modified GNG graph error message

* updated repr for node and graph in GNG

fixed fan computation

changed order for the training agorithms

updated mnist classification tutorial

version 0.6.5 in docs

Version 0.6.4

fixed pep8 error