batch reply functionality
* FEATURES
* Can now reply in batch to a target user with perform_batch_reply().
* You need to supply a callback,
and a target per service,
and optionally some other fields,
and the callback will be used to reply to a number of their recent tweets (number configurable)
* BUGFIXES
* Permit writing lists as JSON from IterationRecord,
needed to support lists of OutputRecord.
* Make _repair a little more robust,
and have it assume less.
* Don't try to _repair legacy tweet records,
this is the wrong behavior and I'm not sure what would happen.
* DEV
* Make all API methods prefer keyword arguments,
though positional arguments will still be allowed.
* All internal methods now use only keyword arguments (or at least most do).
* Use verbose docstrings that can be formatted as documentation,
and eventually I'll do that.
* Expect python3.7 support and update travisCI config appropriately.