Trying to make this merge-able.

* We don't need RequestException anymore.

* I changed TwythonError to raise TwythonRateLimitError instead of
TwythonAPIError since TwythonRateLimitError is more verbose and in the
belief we should deprecate TwythonAPILimit and ultimately remove it in
2.0

* And I updated the version to 1.7.0 -- I feel like development as far
as versioning seems like it's going fast, but versioning is versioning
and I'm following Twitter's rhythm of versioning
<major>.<minor>.<bugfix>, minor changing when minor features or
significant fixes have been added. In this case, TwythonRateLimitError
should start being caught in place of TwythonAPILimit

setup.py

@@ -4,7 +4,7 @@ from setuptools import setup
 from setuptools import find_packages
 
 __author__ = 'Ryan McGrath <ryan@venodesigns.net>'
-__version__ = '1.6.0'
+__version__ = '1.7.0'
 
 setup(
     # Basic package information.