Tracking Previous Requests

Addresses the issue brought up here:
https://github.com/kennethreitz/requests/issues/1929
21m
Update on Tracking Previous Requests

Modified the comment in sessions.py and rewrote the test in
test_requests.py
Merge pull request #2168 from ContinuousFunction/master

Tracking Previous Requests
Added space and sentence case

Added space and sentence case as requested by sigmavirus24.
https://github.com/kennethreitz/requests/pull/2168
Adding my name to authors.
Adding myself to authors.
Adding my name to authors
Documentation update : connection keep alive
Merge pull request #2173 from tychotatitscheff/master

Documentation update : connection keep alive
Cleanup grammar from previous commit.
Merge pull request #2172 from ContinuousFunction/master

Add to authors and fix case