Automatically convert absolute paths to relative when doing "pack" action

[morevnaproject]

This is improvement of #14. The "pack" action can automatically convert absolute paths to relative for processed files.

My proposal is to introduce replace() function. Renderchan will take a list of dependencies of a file (as it's always gets through analyze() function), then for each absolute path entry it calls RenderChanModule.replace("absolute_path", "relative_path) for a given file.

See also WIP #31.

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