Modify 'README.md'
'GPL' is not a valid license in H5P

Remove 'license' from 'h5p.json' and 'library.json' until it can be properly
set. Currently, setting it to 'GPL' will throw an error on upload.
Start building the template

Add a '.scss' file to the library, and include logic for it to compile to a
'.css' file, and a way for H5P to load it.

'interactivetabs.coffee' now builds a more suitable template.