Fixed file:// links in test results

[ryenski]

This commit fixes the "txmt://" backtrace links in the test results window.

Previously, the links would be created like:

# txmt://open?line=5&url=file://app/models/thing.rb

Now, they use the full path, like:

# txmt://open?line=5&url=file:///Users/my_username/Sites/project_name/app/models/thing.rb