Scjson support

PR ready.

Assigned #230 to Jake because there is a bug on scion-core. Otherwise that test will pass.

Currently 156 tests are passing, 53 from W3C.
Closing 8 issues: 5 errors, 3 fails.

Closes #221
Closes #222
Closes #223
Closes #224
Closes #225
Closes #226 
Closes #227 
Closes #228 

I've fixed your previous comment and tested with if-elseif. All "cond" attributes are working as same.

I found a different thing with test344 though:
https://github.com/jbeard4/scxml-test-framework/blob/2.0.0/test/w3c-ecma/test344.txml.scxml
- If a conditional expression cannot be evaluated as a boolean value ('true' or 'false') or if its evaluation causes an error, the SCXML processor MUST place the error 'error.execution' in the internal event queue.

https://github.com/jbeard4/scxml-test-framework/blob/2.0.0/test/w3c-ecma/test309.txml.scxml
- If a conditional expression cannot be evaluated as a boolean value ('true' or 'false') or if its evaluation causes an error, the SCXML processor MUST treat the expression as if it evaluated to 'false'.

It looks like we should choose between raising error or treat boolean value as false. What do you think?