Explicitly ignore containers within navbar for E004

[zacechola]

Fix #215

1. Ignore containers within .navbar
2. Expand search for more than just direct children.

[kkirsche]

indentation is off here. Use 4 spaces per indentation please. This should begin at column 12.

[zacechola]

Argh. Had my editor set for work indentation. Will fix when I get home.

[coveralls]

Coverage remained the same at 100.0% when pulling 6e7f518 on zacechola:nested_containers into cd05e3c on twbs:master.

[hnrch02]

Can be simplified to .not(':has(.navbar)').

[zacechola]

All this time I'd been fighting cheerio with a .find(':not(.navbar)') check. I'll make the change.

[coveralls]

Coverage remained the same at 100.0% when pulling 6eb502e on zacechola:nested_containers into cd05e3c on twbs:master.

[cvrebert]

This logic seems wrong. Consider:

<div class="container">
  <div class="navbar"></div>
  <div class="container"></div>
</div>