add version.py and badges in README

+ add version.py for a explicit list of release history
+ setup.py: grab version number from version.py, instead of manual change
+ README: add badges, to be consistent with other insarlab repos

README: typo fix (insarlab#7)

* README: typo fix

wrapping up for version 0.2.0

+ setup.py: update version number to 0.2.0

+ remove the following unused big test data files and big downloaded GRIB files to save git clone data volume
  - examples/ECMWF/ERA-Int* files (>75 MB)
  - examples/dem* files
  - examples/*.flt files

Update README.md