Moving vendor file to ./vendor.

This is not our file and does not belong here. The ./vendor directory is
spesifically created for this purpose, according to the documentation [1]. See
under 2.1 Asset Organization. «vendor/assets is for assets that are owned by
outside entities, such as code for JavaScript plugins and CSS frameworks.»

[1] http://guides.rubyonrails.org/asset_pipeline.html#asset-organization
Location explanations in application.js.

A few comments explaining where or how each script is provided, as there are
currently three possibilities.
Removing empty files. (They are not necessary)