New release
Improved debugging

 * Improved logging
 * **Deprecated `FastbillHttpError` Execption.** Now only `FastbillResponseError`
   will be raised. `FastbillResponseError` will inherit from `FastbillHttpError`
   for the time being, but catching `FastbillHttpError` is deprecated. Use
   `FastbillResponseError` instead.
 * Improved testcase to check for failing API calls as well.
Moved README.md to README.rst (so that pypi understands it)

 * added changelog to README
New release