Update gitignore.plugin.zsh

Fix URL to gi (gitignore) function in _gitignireio_get_command_list function
Fix remaining broken URL in gitignore function
Merge pull request #2544 from fduch2k/patch-1

Update gitignore.plugin.zsh
Merge pull request #2548 from puffnfresh/gitignore-plugin-url

Fix remaining broken URL in gitignore function
..a fundamental piece of matter.
Merge branch 'master' of github.com:robbyrussell/oh-my-zsh
Merge remote-tracking branch 'upstream/master'