Added optional headers parameter to simple_post()
Updated default parameter
Updated default headers
Merge pull request #101 from sravfeyn/optional-headers

Added optional headers parameter to simple_post()
Updated optional-param default value to None
Merge branch 'optional-headers' of git://github.com/sravfeyn/dimagi-utils into pr-102
don't update dict with None
Merge pull request #103 from dimagi/pr-102

Updated optional-param default value to None
Merge branch 'master' into cached_images