Minor spelling fix.
Correct the terminology used in the value description? Both <http://gpsd.berlios.de/NMEA.html#_mwv_wind_speed_and_angle> and <http://www.tronico.fi/OH6NT/docs/NMEA0183.pdf> state that the "T" value means "True" not "Theoretical". It is assumed they don't disagree with the official, closed specification.
Minor typo fix.
Minor white space fix.
Add test for existing `MWV` sentence parser with supplied sample data.

Conflicts:
	pynmea2/test/test_types.py
Merge branch 'mwv-test' into add-xdr-sentence-support