very large and infinite generators issue

[make-github-pseudonymous-again]

There are some generators that do not work well with infinite (or very large) generators. For some of them it is not so important (product, permutations, combinations ). However, the current implementation of group(by) could be changed to handle these kind of generators more efficiently. For an example of how to do see the Python 3.4 docs.

[make-github-pseudonymous-again]

migrated to https://github.com/aureooms/es-itertools/issues/3