TST: small sigmet ppi and rhi files
TST: io/rsl.py test
TST: graph/plot_rsl.py tests
TST: unit tests for io/grid.py module
BUG: off by one error in phase_proc.py
TST: example single ray ppi radar
TST: unit tests for correct/phase_proc.py module
BUG: off by one error in attenuation.py
TST: unit tests for correct/attenuation.py module
TST: sample interp sonde and aliased radar
TST: unit tests for correct/dealias.py module
TST: fixed broken test in test_mdv.py
TST: removed system_tests

system_tests are now in their own repository at:
https://github.com/jjhelmus/pyart_system_tests
TST: testing data baseline figures