Implement `wp theme get`
Use P2 for tests instead, which won't fatal 3.4 (twentyeleven is already installed)
Merge pull request #703 from wp-cli/theme-get-703

Add `wp theme get`
Merge branch 'master' into fix-theme-path

Conflicts:
	features/theme.feature
Use P2, which isn't conditionally present in some WordPress installs