Ensures DSL files get loaded, even when within jar, called from java

class.

Got to the bottom of [#24](https://github.com/jruby/jrubyfx/issues/24).  I checked on what the value of the `rt` variable in dsl.rb was, in the case that you try to launch a jrubyfx app from java using the embedding api and found out that it was getting set to:

```
jar:file:/home/eric/projects/jrubyfx_projects/jrubyfx_web/hello.jar!/gems/jrubyfx-0.9.2-java/lib/jrubyfx/core_ext
```
And Dir.glob seemed to be choking on that `jar:` at the beginning. So, just added a regex that would remove that if it was at the start and otherwise would leave it as is. Ran the new specs and the run_all_samples which were still fine.