Version 0.6.0 - Adding PDF-417 barcodes & JRuby support

Among other minor cleanup, this pull request adds:

* PDF-417 Barcode generation
* JRuby support file & fix for including the jar (too many ..'s)
* Additional functions for managing metadata on the stamped PDF
* Font enhancements
* Ability to use without rails preserved (removed dependency in intermediate commits)
* README updates
* Version bump