Add sqlite based crl reader/writer

Conflicts:
	Gemfile
update inline documenation of SqliteReaderWriter
fix tests for sqlite < 3.7.11

loading sqlite database for specs from fixture file now.
This simplifies the test setup as well as the reader class itself.
small changes
style fixes
update sqlite readerwriter to use yield
Merge branch 'master' into sqlite-rw

* master:
  ...re-add rbx
fix crl readerwriter test
Merge pull request #89 from reaperhulk/sqlite-rw

SQLite-based CRL Reader/Writer