Create views generator

Running `rails generate category_tree:views` on the main
app will copy the views for categories into the main app
plus all the related stylesheets and javascript files.

Signed-off-by: Joan Tiffany Siy <joan@teamcodeflux.com>
Create controllers generator

Running `rails generate category_tree:controllers` on the
main app will copy the controllers for categories into
the main app.

Signed-off-by: Joan Tiffany Siy <joan@teamcodeflux.com>