Recognize default export and left-hand-side of subscripting operator as usages and nonLocalUsages

Default exports that are merely an identifier, not an expression, and the left-hand-side of the subscripting operator seem to be ignored by usages and/or nonLocalUsages.

import {TypescriptParser} from 'typescript-parser';
new TypescriptParser().parseSource(`
    export default foo;
    bar[baz];
`).then(function(p) {
    console.log(p.usages, p.nonLocalUsages);
});
// Prints [ 'foo', 'baz' ] [ 'baz' ]
// Should print ['foo', 'bar', 'baz'] ['foo', 'bar', 'baz']