Remove irrelevant keywords for grammar

The items removed from the keyword list have never actually been Keywords in JavaScript. In ES3, they were specified as either ReservedWords or FutureReservedWords, but were removed in ES5 and therefore will never actually be a thing in the language.

Signed-off-by: Rick Waldron <waldron.rick@gmail.com>
Merge pull request #15 from rwaldron/remove-irrelevant-keywords

Remove irrelevant keywords for grammar