Add verify_ssl option
added support for url_encoded params and file uploads

Breaking change:
- default is to verify ssl again.

Closes #18

LGTM given by: @marten, @ivdma

Squashed commit of the following:

commit d952366486e5ee71e04d25f1432d18f07846c0cc
    Added options to readme and changelog. clarified skipping of file upload test
commit 40cff8550ac5d7f27f51ee666db7bb7d17bfbf12
    added support for url_encoded params
commit e60a2d62c7334ff2f51b4921df4e8aa5f6393760
    Made it so we can delete vcs cassettes (exept user_digest_hmac)
commit bd4992f8e44b54ad81b6f593c8978faae7f4e788
    Add verify_ssl option