Optional scope (works for expressions without identifiers)
Doc and method reorg
Test argument parsing
Increment after scanning >= and <= (and expect EOF in tests)
Binary expression parsing
Left-hand-side expression parsing
Test unary expression parsing
Confirm whitespace is consumed as expected
Integration testing for unary operators

Only supporting ! at the moment.
Integration testing for multiplicative operators
Integration testing for additive operators
Integration testing for relational operators

No `instanceof` or `in` operator support.