ENH: CF/Radial files follow ARM metadata standards
BUG: gates not collected in masked when reading Sigmet files
ENH: better handling of string arrays
ENH: single string_length dimension in output CF/Radial files
ENH: output CF/Radials files have field_names attribute
BUG: updated example CF/Radial files
ENH: read_sigmet returns time increasing data
BUG: read_mdv returns radar with one dimensional latitude, longitude and altitude data
Merge pull request #83 from jjhelmus/master

Various small enhancements and bug fixes