fixes #64: support spaces in CodeSource URLs
fixes #43: only print stacktrace if debugplugins is enabled
Workaround for issue #69

Made rewriting all system classes optional, to enable easy testing
of whether a given problem is simply that some system classes
are currently being ignored.
Merge pull request #66 from zyro23/issue-43

fixes #43: only print stacktrace if debugplugins is enabled
Merge pull request #65 from zyro23/issue-64

fixes #64: support spaces in CodeSource URLs