Update README
Update README

Add short summary and link to license.

Remove `--save-dev` from `npm install`. This option is used to "save
or update the package version in your main package.json". We don't
want users to change version numbers in the package.json.

Change-Id: I2f9579c42037aff244c6cab71481db2f75391835

mkostikov/tabris-js,eclipsesource/tabris-js,pimaxdev/tabris,eclipsesource/tabris-js,eclipsesource/tabris-js,softnep0531/tabrisjs,pimaxdev/tabris,moham3d/tabris-js,softnep0531/tabrisjs,mkostikov/tabris-js,moham3d/tabris-js