Add support for %k, %l, %u, %W, missing test for %e and extra test for %Z

[himdel]

I'm depending on a few more strftime-format string specifiers - %k, %l are hours without leading zero, %u is day of week with sunday=7 and %W is the week number, this PR introduces them.

Technically, they're not strictly compatible because that would require a leading space for %k & %l but it's the closest we can get without a full rewrite.

Also, the entries for z & Z were out order alphabetically.

This also adds a missing test for %e, an additional date - needed for the leading-zero/nothing difference, and a test that tests that %Z is still passed to moment - according to moment#162, it should keep working when moment-timezone is also used.

[himdel]

(just noticed the extra whitespace change in the spec, I can fix that if you mind..)

[himdel]

For %Z, the other option could be to translate it as [UTC]ZZ instead of z - getting a date with, say.. "UTC-04:00" is better than getting no timezone at all.

[benjaminoakes]

This is great. Thank you for your contribution!

[benjaminoakes]

I've released this as v0.1.4 on npm and bower.

[himdel]

@benjaminoakes No problem, thanks :)