optimize rendering and add additional configuration

- add get_binding method to node to eliminate instance_eval call before rendering template
- pass renderer to nested document so it isn't reloaded (nested table cells)
- make eRuby implementation configurable (Erubis is measurably faster)
- add erubis as development dependency to run test case
- move strscan import to asciidoctor.rb, remove erb import
- push lazy includes through Asciidoctor.include_library & warn if multi-thread env
- make compacting endlines configurable, off by default
- add tests for preserving endlines w/ and w/o compact option enabled
- run tests w/ compact option disabled
- use instance variable references where possible to speed up rendering
- use map instead of passing a proc to invoke render on blocks because it's faster
- additional TomDoc where missing
calculate tablepcwidth more carefully
Merge pull request #85 from mojavelinux/rendering-enhancements

Optimize rendering and add additional configuration