fix crash in peel when the ref is symbolic
Fixed one of the example outputs in the Commit Objects section that
was missing a hash ('#') symbol at the front of it.
Mention bundler's `:submodules` option in the install instructions.

See #218 and #205.
Adding the closing list bracket to the end of an example output.
Adding the missing curly bracket in the string returned by the commit's inspect method.
Bump libgit2
Fix diff tests
bump libgit2 to 6de9b2
bump libgit2 to 4878ea
Cleanup docblocks

* Standardize on 2 spaces for indentation. That's what is used in MRI
docblocks and also what correctly works in both YARDoc and RDoc.
* Enclosing text in "`" characters has no meaning, use "+" instead.
* Fix some other small typos.
More docs for the Index class.
More docs for Index.
More Index docs.
Put call-seq: on the second docblock line.
Fix a typo.
Fix rendering issues in the Repository#reset docs.
Add missing call sequences and re-word a bit.
Switch this around.
Docs for Index.new.
Add Docs for Branch#head? and some other tiny cleanups.