Merge branch 'tracking_branches' of github.com:nvloff/rugged into development
Tidying up the docs for the new branch functionality.
Add documentation for sorting constants.
submodule: add fixtures from libgit2
submodule: add submodule setup to test_helper
submodule: add submodule lookup
submodule: status, reload, add_to_index
submodule: fancy status checks
submodule: extract status symbol definitions
submodule: change status names to be readable
submodule: add .name, .url, .path getters
submodule: add .head_oid, .index_oid, .workdir_oid
submodule: add .ignore
submodule: add submodule.each
submodule: add unmodified? and workdir_dirty?
submodule: add ignore=, cache the ignore rules ids
submodule: add .save
submodule: add submodule.url=
submodule: add .update, update=, reset_update
submodule: add submodule.sync