Improved rand_string generation.
Merge branch 'master' of git://github.com/racker/falcon into pythonic_rand_chars

Conflicts:
	test/helpers.py
refactor(helpers): Change rand_string to be strictly a list comprehension.

Previously, rand_string depended on an iterator class RandChars to generate the
random characters. The rationale for this change is two fold.

1. Reduces code - less code, easier to maintain
2. Increases performance - fewer function calls
Merge pull request #3 from cabrera/pythonic_rand_chars

refactor(rand_string): Change rand_string to be strictly a list comprehension