dygraphs x-range changes
updates to requirements.txt  
implemented date range in dygraphs
Merge remote-tracking branch 'master_repo/master'
changes to hygraph x-range
Merge remote-tracking branch 'master_repo/master'

Conflicts:
	dj_eden_app/hydrograph.py
	dj_eden_app/views.py
merged hydrographs and views
attempted implementation of x-range limits
User specified dates will be used as the plot date ranges. Not working
yet if the date field is left blank on the form.
Merge pull request #11 from ayan-usgs/master

plot x-range changes