Log Message:
Update ruby-pdf-reader to 2.0.0.

v2.0.0 (25th February 2017)
- various bug fixes

v2.0.0.beta1 (15th February 2017)
- BREAKING CHANGE: remove all methods that were deprecated in 1.0.0
- Bug: Support extra encrypted PDF variants (thanks to Gyuchang Jun)
- various bug fixes

v1.4.1 (2nd January 2017)
- improve compatability with ruby 2.4 (thanks Akira Matsuda)
- various bug fixes