Add extra_context parameter and apply override
Test extra_context override
Credit authors
@ryanolson is a cookie monster
Section the extra context docs.
Label clearly as examples. Put in documentation TODOs for after the merge, since out-of-scope.
Add @michaeljoseph's context injection timestamp example from 0d6cca8d6f0aece3744ddc26e135b09287ff2cf5. Expand description to explain more about how it works.
Break extra_context test into 2 tests, to cover both combinations with default_context.
Test cookiecutter() with no_input+extra_context.
Test cookiecutter() with normal input + extra_context.
Add changes to history.
Merge pull request #274 from audreyr/audreyr-extra-context

Merging this in, all tests pass. Tomorrow evening I hope to take a stab at covering tests for #273 and #275. As well as working on additional documentation and example usages of this feature.
Use a utility function to cleanly read input from the user
Add a docstring for read_response
Fix a new test to patch read_response