Fixed Gruntfile.js to allow build

[orentrutner]

This addresses issue #3 Unable to build. It implements @Rheeseyb's two changes, and adds another one to address the failed doc generation:

• 'tsc' executable in the gruntfile was modified to 'node_modules/.bin/tsc'.
• 'commonjs' was changed to 'amd'. I don't know if there are negative consequences to that anywhere, but it seems to work in a straightforward manner with my browser app.
• added a replacement rule to address syntax that was tripping the doc generator. I just followed the convention in that part of the gruntfile.

[IjzerenHein]

Hi, thanks for these contributions, I've merged the changes into the master branch and updated the toolchain dependencies to their latest versions.