Clone and Init should take in RepositoryOptions

[haacked]

The Repository ctor has an optional argument RepositoryOptions. However, there's a couple of places that create new instances of Repository and don't allow us to pass in a RepositoryOptions.

Repository.Init and Repository.Clone. They probably should. In our case, we need to pass in a custom global git config file path everywhere we use Repository.

[dougrathbone]

I'd also love a depth option for the clone (this probably isn't the right place to bring it up).

#229

[Saaman]

I will work on this one...

[ben]

Both of these are going to take some work in libgit2. I'm rounding up all the API-breaking changes over at libgit2/libgit2#1142; feel free to weigh in there.

[nulltoken]

@haacked I think @Saaman's addition should fit your need ;-)

[haacked]

👍 This looks great! Thanks!

[nulltoken]

Guys, sorry to dig up this thread, but I'd like you to peek at #453.

This new PR directly impacts back on this issue.