Support windows

Trying to get this plugin to work under windows. These changes help me to make it work with JRE 1.7.

There are three problems:
 - Couldn't find path to phpmetrics.phar because of the white space
 - Couldn't use path to phpmetrics.phar because of wrong format
 - Couldn't open the file in the browser because of wrong URI-format

This PR fixes the problems, but I'm not sure whether it does run under linux / JRE 1.6. Perhaps you could try?