Use NPM bin directory in Makefile.

The Makefile was not calling explicitly the scripts installed by NPM.
Merge pull request #188 from rocha/use-npm-relative-paths

Use NPM bin directory in Makefile.
Updated charting tooltips to include header and updated labels.
Merge pull request #189 from edx/dsjen/demographic-tooltips

Updated charting tooltips to include header and updated labels.
WIP