* Increase test coverage
* Test for error when binding `this` in destructuring pattern
* Ignore coverage of inAsync check in parseAwait - already checked externally
* Ignore coverage of default case in checkPropClash
* Remove unused parameter isAsync from parseParenAndDistinguishExpression
* Ignore coverage of an `else` branch in flowParseTypeParameterDeclaration
* Flow: remove unused parameters to flowParseTypeAnnotatableIdentifier
* Flow: ignore coverage of pass-through throw statement in parseConditional
* Flow: Add test for error on property with type param
* Flow: ignore coverage of pass-through throw statements in parseMaybeAssign, parseArrow
* Add test for error on XML-style comment in module code
* Update test for error on method in object pattern
* Test for error: "Only '=' operator can be used for specifying default value"
Expanding on #150, this allows `unexpected()` to accept the expected token type instead of a message string.
This overload is then used in a couple more places (that independently implement a logic similar to `expect()`'s) to construct an `Unexpected token, expected FOO` message.
* This removes the exponentiationOperator as it is now in es2016
* Remove from tests
* Remove asyncFunctions and restructure test dirs
* Remove trailingFunctionCommas
