codec/line: do charset conversion on flush

Add tests to verify line codec does charset conversion on flush.

Fixes #1520
Remove the "how to get help" banner because nobody reads it.

There's several indications that folks don't actually read this banner
when unexpected errors occur. If nobody's reading it, then it's just
wasting space in the output.

I would cite references, but will not because there's no need to shame
anyone.

Fixes #1442
gem bundling refactor

update jruby jar to 1.7.15

pinned i18n dependency and cosmetic cleanups

new generated Gemfile lock

refactor gem bundling using stadalone setup & use standard Gemfile with gemspec

update to jruby 1.7.16 and remove jar-dependencies, bouncy-castle-java, jruby-openssl from gemspec

get ready for future plugins mechanism
PoC adding metadata support

For #1834
Add 'metadata' setting for getting metadata on rubydebug
Improve spec subject
Fix failing tests

Also use constant for @metadata and [@metadata]
Add more tests