bump gulp
remove process.env.port from config now that it's in gulp
improve CSS for site navigation bar (bug 1082161, bug 1083613, bug 1083614)

* remove unused rules, optimise selectors, and make things more OOCSS-y
* improve navigation hover states (bug 1082161)
* use CSS instead of JS to toggle category drop-down on desktop (bug 1083613)
* add borders to desktop navigation items (bug 1083614)
* fixed CSS to actually hide the link outlines on focus
* remove `cur-cat` class and use more descriptive classes
* remove specificity all over the space to reduce complex cascading
* considerable cleanup to `sprite-background-position` for category icons
Merge pull request #727 from cvan/nav-tweax

improve CSS for site navigation bar (bug 1082161, bug 1083613, bug 1083614)
bump gulp for serve speed
use faster css gulp watcher (bug 1091421)
bump gulp for catching stylus errors better
remove underscore dep
farewell official nunjucks, t'was but a dream
update gulpfile comments
Commit from Mozilla Verbatim by user selim@selimsumlu.com.tr.: 297 of 335 strings translated (0 fuzzy).
Merge branch 'master' of github.com:mozilla/fireplace
Commit from Mozilla Verbatim by user selim@selimsumlu.com.tr.: 325 of 335 strings translated (0 fuzzy).
bump gulp
remove unused 60px brand icons (bug 1090564)
pull common makefile directives from marketplace-template (bug 1092158)
remove unnecessary apps.getInstalled call from tarako (bug 1092463)
Commit from Mozilla Verbatim by user besnik@programeshqip.org.: 330 of 335 strings translated (1 fuzzy).
Commit from Mozilla Verbatim by user besnik@programeshqip.org.: 330 of 335 strings translated (1 fuzzy).
Merge branch 'master' of github.com:mozilla/fireplace