repository: fix some golint warnings
repository: improve some docs
repository: more documentation improvements
repository: s/Url/URL/

This is golint speaking, not fsouza :-)
repository: add docs for the Repository type

Now golint is happy.
repository: receive the name of the repository in Remove
api: s/Url/URL/
api: fix code that used repository.Remove
repository: add Rename function

Related to #85.
api: add handler for renaming repositories

Related to #85.
webserver: map RenameRepository handler

Closes #85.