Allow for request timeouts to be specified

By default requests has no timeout, this is risky when using it from a server backend. Similar to the verify that got exposed recently, this adds a timeout parameter, which defaults to the requests default of None, to refresh_token and fetch_token.
Update license to 2014
Merge pull request #145 from singingwolfboy/2014

Update license to 2014
Revert "Allow a base_url parameter for sessions"

This reverts commit 0c4c362fdfcfe5e0024f754314957f4d1badef4b.
Remove base_url from HISTORY
Merge pull request #148 from singingwolfboy/remove-base-url

Remove base_url feature
Merge branch 'patch-1' of https://github.com/RR2DO2/requests-oauthlib into RR2DO2-patch-1

Conflicts:
	requests_oauthlib/oauth2_session.py
Merge branch 'RR2DO2-patch-1'
[FIX] ImportError: cannot import name to_native_string

`requests` lib version should be >= 2.0.0 for `requests.utils.to_native_string` to be available

See: http://stackoverflow.com/a/24955127/798575
Merge pull request #151 from alanjds/patch-1

[FIX] ImportError: cannot import name to_native_string
v0.4.2