Merge pull request #1 from ayan-usgs/master

added test for dataframe creation
Merge pull request #2 from ayan-usgs/master

added docstrings
Merge pull request #3 from ayan-usgs/master

more documentation
Merge pull request #4 from ayan-usgs/master

changes to conf.py
Merge pull request #5 from ayan-usgs/master

small documentation changes
Merge pull request #6 from ayan-usgs/master

updated requirements.txt and added optional-requirements.txt
added openpyxl to setup.py