BUG: plotting volumes with a single azimuth/elevation
ENH: aux_io.read_pattern

* Function for reading files from the PATTERN project X-Band radars.
Merge pull request #187 from jjhelmus/read_pattern

ENH: Read files from the PATTERN project
Add Grid datetime routine

I am adding a datetime_from_grid function to the datetime_utils module.
This function should return the datetime corresponding to the volume
start time of the Grid.