Adafruit-circuitpython-minimqtt

**Improvements for KeepAlive**
* `keep_alive` is now an init kwarg
* The `loop` method now checks the time and sends a PINGREQ (expecting a PINGRESP, this is handled in the `ping()` method) to the server if the time elapsed is greater than or equal to the provided `keep_alive` value.

**Network Management Improvements**
*`loop_forever` now calls `loop` instead of `_wait_for_msg`. Also now handles network control, for both the socket and the NetworkManager (currently only the WiFiManager) objects.
* Properties for network management (`is_wifi_connected`, `is_sock_connected`) have been added as well as additional management for both the socket and ESP32SPI wifi module (`reconnect_socket`, `reconnect_wifi`)


To use in CircuitPython, simply install the [Adafruit CircuitPython bundle](https://github.com/adafruit/Adafruit_CircuitPython_Bundle).

To use in CPython, `pip install adafruit-circuitpython-minimqtt`.

Read the [docs](http://circuitpython.readthedocs.io/projects/minimqtt/en/latest/) for info on how to use it.

This release fixes `connect()` for use with large (>127 bytes) payloads such as a long password (JSON Web Tokens), client identifier, or last-will message.

* The remaining length calculation previously used by this library has been removed in favor of using the algorithm described by the MQTT V3.1.1 specification (https://docs.oasis-open.org/mqtt/mqtt/v3.1.1/os/mqtt-v3.1.1-os.html#_Toc398718030).
* Default `keepalive` value increased to 60 seconds to ensure the MQTT broker rejects incorrect connections, instead of hanging.

To use in CircuitPython, simply install the [Adafruit CircuitPython bundle](https://github.com/adafruit/Adafruit_CircuitPython_Bundle).

To use in CPython, `pip install adafruit-circuitpython-minimqtt`.

Read the [docs](http://circuitpython.readthedocs.io/projects/minimqtt/en/latest/) for info on how to use it.

Initial release of MiniMQTT, a MQTT Client Library for CircuitPython.

This library aims to be independent of network hardware. However, at this time the MiniMQTT library is only available for CircuitPython devices connected over WiFi.

This library is based off previous work performed by pfalcon on [uMQTT](https://github.com/micropython/micropython-lib/blob/master/umqtt.simple/umqtt/simple.py) (and the [umqtt port to ESP32SPI by beachbc](https://github.com/beachbc/esp32spi_mqtt)). MiniMQTT's primary difference from uMQTT is it uses calling conventions and method names similar to The Eclipse Foundation's [Paho.Mqtt.Python](https://github.com/eclipse/paho.mqtt.python/).

To use in CircuitPython, simply install the [Adafruit CircuitPython bundle](https://github.com/adafruit/Adafruit_CircuitPython_Bundle).

To use in CPython, `pip install adafruit-circuitpython-minimqtt`.

Read the [docs](http://circuitpython.readthedocs.io/projects/minimqtt/en/latest/) for info on how to use it.