Make no-namespace rule fixable

[TrevorBurnham]

This PR adds support for --fix to the no-namespace rule, in the case where all references to the namespace can be statically resolved:

Input

import * as foo from 'foo';
florp(foo.bar);
florp(foo.baz);

Output

import { bar, baz } from 'foo';
florp(bar);
florp(baz);

The motivation for this is to make it easier to opt in to no-namespace in codebases that are already using this pattern. It sure beats having to do it all by hand! 😄

Note that this will only work under ESLint 5+, as older versions don't allow for traversing upward from variable references. That is, in this code identifier.parent is undefined. I haven't been able to figure out a good way to support this under ESLint 4 (let me know if you have any ideas!), so I've added a note for this in the rule's documentation.

[coveralls]

Coverage decreased (-0.1%) to 96.319% when pulling d030d8e on TrevorBurnham:no-namespace-autofix into 3704801 on benmosher:master.