Update l20n.js
Add configuration options

Allow to set the localStorage key, the property name on the $rootScope
and the function name to change locale.
Don't add anything to $rootScope by default; export the changeLanguage function
README: correct info about compatible l20n versions
Dump jsHint in favor of ESLint and JSCS
Remove copyright headers
Tabs -> spaces
Travis: remove empty before_install block
Rename grunt-jscs-checker to grunt-jscs (& update it)
Change Travis badge from PNG to SVG
Test on one Node version; it's a frontend package
Add vendor/** to .eslintignore; update grunt-eslint
WIP