Implement hash and array literal syntax

[wycats]

This is an initial implementation of array and hash literals.

Of note:

• The hash literal syntaxes ((key1=value1 key2=value2) and {{key1=value1 key2=value2}}) are currently syntax errors, so they can be added without breaking changes or any form of opt-in.
• The array literal syntax ([a b c]) is ambiguous with the this-less escaped property path ([a b] currently means this.[a b], which translates to this["a b"] in JavaScript).

The latter form is disallowed in Ember, which does not support the implicit this form.

To avoid breaking existing consumers, this PR makes the array-literal syntax opt-in via a parser option.