Gzip content and use gzip content-encoding.
Tests for gzip content.
Add notes about gzip content types in docs.
Checking explicitly for gzip content encoding before gzip the content.
Merge pull request #89 from michelts/gzip-content-type

Add support for gzipped content types when using Pyrax.
Merge remote-tracking branch 'upstream/master' into pyrax-version

Conflicts:
	docs/index.rst