Pynsq

This is a bug-fix release addressing a few issues in `Writer`.

* 48 - fix writer encoding issues
* 47 - fix writer uncaught exception when no connections to publish to
* 45 - fix writer id property

This release drops the concept of "tasks" in `Reader` (in favor of a single message handler). This
greatly simplifies internal RDY state handling and is a cleaner API as we head towards 1.0.

These changes modify the public API and break backwards compatibility. To ease the transition we've
added a `LegacyReader` class that accepts the previous version's arguments and facilitates
instantiating new `Reader` instances for each task with the same automatic channel naming
conventions.

We suggest you begin to migrate towards using the new API directly (`LegacyReader` will not be
in the 1.0 release), but for now the upgrade is as simple as:

from nsq import LegacyReader as Reader

Finally, TLS support is available via `tls_v1` and `tls_options` params to `Reader` (available in
`nsqd` as of `0.2.22+`).

* 42 - TLS support
* 39 - distribute requests to lookupd
* 38 - fix edge case where conn would never get RDY; RDY fairness when conns > max_in_flight
* 36/37 - refactor internal connection, backoff, and RDY handling
* 29/34/35 - refactor public API (drop "tasks"); improve RDY count handling
* 28/31 - improve backoff handling

* 25 - add Writer
* 24 - add is_starved to Reader

* 23 - fix Message export, cleanup IDENTIFY response logging

* 22 - feature negotiation (supported by nsqd v0.2.20+)
wait 2x heartbeat interval before closing conns
more logging improvements
* 21 - configurable heartbeat interval (supported by nsqd v0.2.19+)
* 17 - add task to all connection related logging; ensure max_in_flight is never < tasks
* 16 - always set initial RDY count to 1
* 14 - automatically reconnect to nsqd when not using lookupd
* 12 - cleanup/remove deprecated async=True
* 9 - redistribute ready state when max_in_flight < num_conns

* 10 - fix parameter type for REQ
* 8 - add tests
* 6 - fix TOUCH; deprecate `async=True` in favor of always using message instance methods