new backend status

[Ryan Brown]

I think we're getting close to being able to release an RC using the new backend.

More than 95% of tests are passing, the remaining failures are:

 - generics aren't implemented yet. I plan to tackle this next

 - dynamic isn't implemented yet

 - Two tests have different behaviour, I think the new behaviour is correct. 

 (test_rescue_scope and test_interface_implementation_with_array_params_requires_type_information)

 - There's one failure I can't reproduce outside the tests.

There's only a few remaining things left to port now to have a fully functional mirahc that doesn't depend on jruby:

 - argument parsing

 - error reporting (Mostly implemented, just need to convert ErrorTypes to Diagnostics)

 - macro compilation (The pieces are all there, just need to implement a couple interfaces to tie everything together)

The pure-mirah mirahc compiles 'hello world' in 0.5 seconds on my machine, vs 8 seconds for the jruby mirahc.

[John Woodell]

This is great news!