Make jstax work again; make nokogiri the jruby default
Nokogiri SAX parser, add :processing_instructions to list of ignored methods.

I don't entirely understand what this code does, but new version of nokogiri
seems to have more methods that need to be ignored here. Don't entirely
understand the architecture though.
JRubySTAXReader, require 'java' needed for jruby 1.6
Merge branch 'fixjstax'
remove duplicate catch of #processing_instruction, already doing it in method_missing with the others
Marc::Reader, force_encoding(binary) to avoid byte-vs-char counting issues when doing byte arithmatic.

For some reason only causes a test failure in jruby 1.7, not mri. I dunno.
bump to 0.5.1 -- fixes for new versions of jruby, nokogiri, and other dependencies