examples/diff: Add minimal, patience diff options.

- Add minimal, patience diff options to diff example. libgit2
  `diff_xdiff.git_xdiff_init` already supports these flags, so
  no additional change is necessary.
- Remove minimal and patience flag addition from project list.
Fixed missing error check on call to git_remote_download in git_remote_fetch. Moved error check to statement following git_remote_disconnect so that the disconnect happens regardless of the result of the download call.
Merge pull request #2161 from softwarenerd/softwarenerd

Fixed missing error check on call to git_remote_download
Merge pull request #2160 from modocache/examples-diff-add-patience-and-minimal

examples/diff: Add minimal, patience diff options.