Ruby script to test grammars

This is similar to org.antlr.v4.runtime.misc.TestRig.
Clean up RubyTarget code

remove redundent code
fix formatting.
fix semantic predicate blocks
python extend -> Ruby concat
comment out code from 4.4.1

There was code I coppied from 4.4.1 thinking it would fix a problem.
But it didn't fix it and caused other problems since it is not fully
implemented. I'll do a 4.4.1 pass later
makefile cleanup

- add depends
- add new targest to test Tnt grammar
remove redundent code
Gemfile for bin scripts
Cleanup output