Add METAR/SPECI/TAF decoder

[kevinelliott]

Ability to decode arbitrary strings from standard METAR/
SPECI/TAF formats to an object containing breakdown of report. This decoder can be used to decode METAR reports that come in via messages, or for sites like Airframes and AcarsHub to allow users to do decodings of copy&pasted reports in their UIs.

METAR
Meteorological Aerodrome Report is standardized by ICAO worldwide. Contains information on the current weather conditions of the facility releasing the report.

TAF
Terminal Aerodrome Forecast is a report released by large airports that summarizes the weather forecast for the area covered by five statute miles from the location of the airport. Valid for 24-30 time periods and is updated 4 times a day typically.

Both METARs and TAFs are automatically retrieved from NOAA automatically and published here:
https://github.com/airframesio/data/tree/master/json/noaa

[kevinelliott]

Assigning this to you @makrsmark if you are up to it!