Update readme to guide people to use StackOverflow.

Hopefully this will stop people from sending us emails with their questions.
Merge pull request #334 from libgit2/arthur/update-readme

Update readme to guide people to use StackOverflow.
Settings: add support for search paths

Let the user set and get the config search paths
Merge pull request #337 from libgit2/cmn/search-paths

Settings: add support for search paths
change the repository clone_at option to checkout_branch to match
libgit2 and assign it. add tests for checkout_branch
Improved code based on comments from @arthurschreiber
Remove the test with ssh credentials and branch since it breaks the travis build. Added assertion to test_clone_with_branch
Merge pull request #339 from albertsun/repository-clone-at-checkout-branch

Rugged::Repository.clone_at checkout_branch option
Use `StringValueCStr` instead of `StringValuePtr`

`StringValuePtr` returns a non-zero terminated `char *`, but we need to pass a zero-terminated `char *` to libgit2.
Update to latest libgit2
Merge pull request #340 from libgit2/cmn/updates

Update to latest libgit2
Repository: add #merge_analysis

Determine what merge-tangential actions can be performed.
Extended docs for `Repository#merge_analysis`.
Merge pull request #341 from libgit2/cmn/merge-analysis

Repository: add #merge_analysis
Merge file API support
Tweaks based on feedback
Merge pull request #322 from GoBoundless/merge_file_support

Merge File API + Updates to support new libgit2 git_merge API
`rb_external_str_new` -> `rb_str_new`
Update to latest libgit2.
Merge pull request #344 from libgit2/arthur/update-libgit2

Update to latest libgit2.