Added link to wiki page for plugins to README.

The wiki is more readable than going to the plugins directory.

README.textile

@@ -59,7 +59,7 @@ If you installed manually or changed the install location, check ZSH in ~/.zshrc
 
 h2. Usage
 
-* enable the plugins you want in your @~/.zshrc@ (take a look at @plugins/@ to see what's possible)
+* enable the plugins you want in your @~/.zshrc@ (take a look at the @plugins/@ directory and the "wiki":https://github.com/robbyrussell/oh-my-zsh/wiki/Plugins to see what's possible)
 ** example: @plugins=(git osx ruby)@
 * Theme support: Change the @ZSH_THEME@ environment variable in @~/.zshrc@.
 ** Take a look at the "current themes":https://wiki.github.com/robbyrussell/oh-my-zsh/themes that come bundled with _Oh My Zsh_.