Support for Lat/Lon/Elevation Data

[brentru]

Addresses issue: #9
Adafruit Forums Discussion: https://forums.adafruit.com/viewtopic.php?f=56&t=82937

Scope:

• Added method send_location_data in client.py, supported by api-v2 branch
• Modified model.py to support additional DATA_FIELDS per api v2 for lat, lon, ele.
• Test example for sending location added in examples/api/location.py

[brentru]

RX/TX test successful: io-client-python/examples/aio_basics/adafruitio_04_location.py

Sending Values to location feed...

    Value:  5
    Lat:  40.67619000000001
    Lon:  -74.10533399999998
    Ele:  11

Data from Adafruit IO Feed:

    Value: 5
    Lat: 40.67619000000001
    Lon: -74.10533399999998
    Ele: 11.0

Merging into api-v2-master...