Splitting index and group html pages.

To have forward backward navigation from the page of repository groups to the
page of repositories in a given group.
Splitting the behaviors of groups and repos.
Fixed jQuery envelop function. Added JSON.

Put in a JSON file the cached response from github.
This second one is mostly to facilitate development.
Clean up duplicate functions.

Cleaned up group.html and index.html to remove functions from one
file that were relocated to the other.
Added category property to repos.

Inserted from the category of the corresponding group.
Unescape URL to restore spaces.

Used the unescape function to restore spaces in group names.
Merge branch 'groups_page'