Install the latest version of TogglDesktop.app

Presently puppet-toggl downloads an outdated version of the TogglDesktop.app (4.94); unfortunately this older version also doesn't have a built-in updater that updates to the latest version (6.3). The latest download links are described here:
http://support.toggl.com/toggl-on-my-desktop/#download 

Because of a flaw in puppet's appdmg provider, the generic "latest" URL won't work as "source" won't work until puppetlabs/puppet#2249 has been resolved & released and our-boxen's Gemfile has been updated accordingly.

In the meantime I've updated the provider with a hotlink to the current version. It also removes an appdmg "cookie" that Puppet sets, which would prevent updating an existing installation with the latest version.

Additionally a recent change to rubygems affected the running of tests with ruby 1.8.7 on travis-ci. I've included the fix described in rubygems/rubygems#763

You should be able to test this by switching the Toggl line in your Puppetfile to the following:
```
github "toggl", "1.0.2.907", :repo => "webbj74/puppet-toggl"
```