OS X Helpers

Add helper aliases for show/hide files. Add helper alias to recursively delete
.DS_Store files.

plugins/osx/osx.plugin.zsh

+alias showfiles='defaults write com.apple.finder AppleShowAllFiles TRUE; killall Finder'
+alias hidefiles='defaults write com.apple.finder AppleShowAllFiles FALSE; killall Finder'
+
+# Recursively delete .DS_Store files
+alias rm-dsstore="find . -name '*.DS_Store' -type f -delete"
+
 function savepath() {
   pwd > ~/.current_path~
 }