Fix Rspec deprecation warning

Supplying a particular Exception with `to_not` has been deprecated.
Factor out some duplication
Reduce response duplication
Fix README formatting
Add support for etags
Merge pull request #8 from jonallured/fix-rspec

Fix Rspec deprecation warning
Merge pull request #9 from jonallured/etags

Add support for Etags

@jonallured This is awesome!
I just tested it and works like a charm... and just as you mention in the updated `README`, as it supports Gzip now by passing the corresponding header.. I'm thinking on making it the default header to send... response speed is better when passing this option.
:smile:
Updates README and CHANGELOG. Bumps version to 0.1.0
Enables Gzip compression by default. Small version bump to 0.1.1