Library functions aren't consistent with design guide

[caternuson]

Ref: http://circuitpython.readthedocs.io/en/latest/docs/design_guide.html#sensor-properties-and-units

Currently have accelerometer and magnetometer. These should be acceleration and magnetic. Suggest keeping current ones and adding in the new ones.

Also, accelerometer is returning a list, not a tuple.

[ladyada]

ooh good catch - i'm ok with a breaking change since this is a very new driver
@kattni wanna take this one? :)

[kattni]

Sure thing!

@ladyada to clarify: you'd rather simply alter what's there and remove the incorrect naming?

[ladyada]

yes that is correct - thank u kattni :)

[caternuson]

Closing. Fixed by #3