Various cleanups to Ubuntu installation instructions:

* Avoid editing /etc/apt/sources.list add nginx repo, instead create
  /etc/apt/sources.list.d/nginx.list

* Avoid editing /etc/nginx/nginx.conf, instead put server_name_hash_buckets
  setting into discourse.conf

* Proper-case Discourse when it is referring to the product name, so that all
  the lowercase references are to the user created during the installation
Address @Supermathie's concerns in PR1430
Simplify characterCode lookup

Reduce String.fromCharCode that can’t be optimized by the minifier.
Combine single path conditional
Remove unused variable

It is only set to empty then passed
updated spanish translation
Add `bookmarked` class to bookmarks button. Also remove duplicated code,
use fewer observers.
Merge pull request #2071 from nschonni/autocomplete-js-cleaning

Autocomplete js cleaning
FIX: Only add `home` class when there is no badge
Create a cold age helper, make sure the first age column is strictly
`created_at`, add cold to the second column.
FIX: Suggested Topics had a hardcoded 5 and was ignoring the
SiteSetting
FEATURE: top is now by default in the top menu
fixing regression, adding max-height to #site-logo
Merge pull request #2101 from awesomerobot/master

fixing regression, adding max-height to #site-logo
PERF: Don't blur all elements on a page
add calendar icon to best of
add envelope icon to invite friends default btn
fixing the remnant borders left on the header buttons
reduce docked header title font size slightly
JSHint QUnit helpers

- Don’t redefine controller
- Mark all functions as exported
- Mark the QUnit asyncTest as a global function