move reset params to post() and get() methods
Refactor bearer-token methods
Also fetch and process response headers

Headers can be useful to avoid extra requests for rate-limit info.
*   x-rate-limit-limit  (max request per period)
*   x-rate-limit-remaining  (remaining this period)
*   x-rate-limit-reset  (start of next period, UTC timestamp)
Merge branch 'master' of https://github.com/GDmac/TwitterOAuth into master_up
Merge pull request #11 from GDmac/master

Refactor bearer-token methods, and fetch headers