Replaced legacy Diff commands with Fugitive buit-in analog
Replaced legacy PullRequestDiff body with Fugitive buit-in analog

But leave a function in the plugin because it contains some parsing
logic anyway. Also, don't add "All commits" after request-pull output.
Commits are observeable in related files by Gblame anyway.
Function GlopenFromDiff

Allows to jump from diff to corresponding file, containing changed code
under cursor.
Addd GlopenFromDiff function to open files from 'diff' outputs
Version bump 0.0.2