Remove unneded freeze

* All constants in this file get frozen automatically.
minor spec fixes
first take on 1.9-style hashes
extra colon fix & cleanup
Improve documentation of constants
Remduce feature envy and conditional chaining
Fix unsafe symbol hash key emitter and some docs
Add DBL_QUOTE constant
Depend on node type instead of emitter class
Update state of project in README
Merge upstream/master into emitter_fixes

Conflicts:
	lib/unparser/constants.rb
Typo
Merge pull request #18 from 7even/emitter_fixes

Emit 1.9 style hashes when possible.
Remove mode suffixes for rubies on travis
Bundle rubysl to have access to rbx standard library