fix the open command in linux using xdg-open
Merge pull request #1849 from lemieux/master

Fix for Jira plugin on Linux
Merge branch 'master' of https://github.com/robbyrussell/oh-my-zsh
Update README.textile

Add upgrade command to docs. I canceled the prompt once and went hunting for this so I could upgrade.
Merge pull request #1870 from mfrobben/patch-1

Update README.textile
Merge branch 'master' of https://github.com/robbyrussell/oh-my-zsh
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