Initial C port working

TODO
make a generic C rb tree library
change all keywords to lower case (and tests)
add goto keyword
update README with grammar
Make expressions recursive
Add support for different variable types (real numbers to start)
etc. ..
Lots of changes, updates, improvements

Expressions are recursive now and also include the logical/comparison
operators with correct operator precedence etc.

All keywords are lower case.

New data structures (definitely still needs work and will expand/adapt
as new features are added)

Added beginnings of support/framework for other types (not just int)

Reads all tokens at once to allow easier and arbitrary
backtracking/lookahead/debugging during parsing

Other stuff I'm forgetting.  See README.md