Merge pull request #11 from ayan-usgs/master

plot x-range changes
Merge pull request #12 from ayan-usgs/master

matplotlib no longer connects points, unspecified date ranges are now okay on the plots
Merge pull request #13 from ayan-usgs/master

improved implementation of date ranges in matplotlib
SQL for computed flags and daily means.
Merge branch 'master' of https://github.com/USGS-EDEN/EDEN-hydrograph-data.git
Testing for compound queries.
Single-gage methods for hourly and daily data.
Add computation of line modes from flag.
Will depend on splitting data series by flag character.
Remove unused method.
Be more careful about memory for csv writing.
Merge remote-tracking branch 'master_repo/master'
updates to dygraph javascript and implemented headers in data downloads