Added Contextual Help to the Demographics Pages
Fill enrollment trend with previous day's count.
Merge pull request #176 from edx/dsjen/fill-enrollment-trend

Fill enrollment trend with previous day's count.
Merge pull request #175 from edx/demographics-help

Added Contextual Help to the Demographics Pages
Corrected link to Developer's guide

@mhoeber , @stroilova
Title, link to dev guide updated
Merge pull request #177 from edx/ahodges/doc/DOC491bis

Corrected link to Developer's guide, fixes DOC-491
Displaying Enrollment Mode on Enrollment Activity Page