.osx: Only install custom Terminal profile once

Closes mathiasbynens#336 and mathiasbynens#337.

.osx

@@ -543,10 +543,14 @@ sudo mdutil -E / > /dev/null
 defaults write com.apple.terminal StringEncodings -array 4
 
 # Use a modified version of the Pro theme by default in Terminal.app
-open "${HOME}/init/Mathias.terminal"
-sleep 1 # Wait a bit to make sure the theme is loaded
-defaults write com.apple.terminal "Default Window Settings" -string "Mathias"
-defaults write com.apple.terminal "Startup Window Settings" -string "Mathias"
+TERM_PROFILE='Mathias';
+CURRENT_PROFILE="$(defaults read com.apple.terminal 'Default Window Settings')";
+if [ "${CURRENT_PROFILE}" != "${TERM_PROFILE}" ]; then
+	open "${HOME}/init/${TERM_PROFILE}.terminal";
+	sleep 1; # Wait a bit to make sure the theme is loaded
+	defaults write com.apple.terminal 'Default Window Settings' -string "${TERM_PROFILE}";
+	defaults write com.apple.terminal 'Startup Window Settings' -string "${TERM_PROFILE}";
+fi;
 
 # Enable “focus follows mouse” for Terminal.app and all X11 apps
 # i.e. hover over a window and start typing in it without clicking first