Ignore some jbundler related working state
Support passing in a topic for every #push in MRI

This commit also fixes a memory leak with the JRuby version of the gem where we
were not properly cleaning up children objects and holding onto references of
them forever

Fixes #46
Add a much more verbose download_file_http method for mini_portile

This should help isolate the bug we're seeing in #40 which seem to stem from
GitHub serving invalid packages
Avoid adding non-existent children to our internal list.

This really only affects testing where we might be returning nil after a
push_single expectation has been met
Merge pull request #51 from rtyler/mri-multi-topics

Multiple topics for MRI