Support JSON within YAML

Requirements

Filling out the template is required. Any pull request that does not include enough information to be reviewed in a timely manner may be closed at the maintainers' discretion.
All new code requires tests to ensure against regressions

Description of the Change

JSON is YAML, so support it.

Alternate Designs

None.

Benefits

JSON syntax will be tokenized correctly.

Possible Drawbacks

Should be none.

Applicable Issues

Fixes #5

/cc @envygeeks, @szhu please test this PR out. I need to know if I need to include JSON support in other places. For example, should the inside be tokenized as JSON here, or as a YAML unquoted string?

a key:
 - { "some_json": "whoa" }

atom / language-yaml