Fixed typos/copyediting

Fixed minor typos and copyediting errors in documentation and docstrings.

Affected files:
  - README.rst
  - docs/source/news.rst
  - docs/source/2014-news.rst
  - docs/source/faq.rst
  - docs/source/settings.rst
  - gunicorn/config.py

Possible errors left uncorrected in gunicorn/config.py (and docs/source/settings.rst):
  - an incomplete sentence in the description of LimitRequestFieldSize 
  - ambiguous phrasing in the description of ForwardedAllowIPS
  - ambiguous phrasing in the description of ProxyAllowFrom