Support single redis DB.
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
Locate the Puma config file.
Update puma.rb
Add Global Keyboard Shortcuts

Not all of these have been fully implemented yet.

**Jump To**
* `g` then `h` - Home (Latest)
* `g` then `l` - Latest
* `g` then `n` - New
* `g` then `u` - Unread
* `g` then `f` - Favorited
* `g` then `c` - Categories List

**Navigation**
* `u` - Back to topic list
* `k` / `j` - Newer/Older conversation or post
* `o` or `Enter` - Open selected conversation
* <code>`</code> - Go to next section
* `~` - Go to previous section

**Application**
* `c` - Create a new topic
* `n` - Open notifications menu
* `/` - Search
* `?` - Open keyboard shortcut help

**Actions**
* `f` - Favorite topic
* `s` - Share topic
* `<Shift>` + `s` - Share selected post
* `r` - Reply to topic
* `<Shift>` + `r` - Reply to selected post
* `l` - Like selected post
* `!` - Flag selected post
* `b` - Bookmark selected post
* `e` - Edit selected post
* `d` - Delete selected post
* `m` then `m` - Mark topic as muted
* `m` then `r` - Mark topic as regular
* `m` then `t` - Mark topic as tracking
* `m` then `w` - Mark topic as watching
Add a few extra ProxyPass calls

These avoid a lot of 404 errors, and things like the style editor not working because the browser can't reach scripts, etc.
Fix unused parameter
Update client.it.yml
Update client.zh_CN.yml
Update french locales
Merge pull request #1789 from ofgeek/patch-1

Update client.zh_CN.yml
Merge pull request #1787 from Baldrick44/master

Fix unused parameter
Merge pull request #1765 from thisgeekza/patch-1

Add a few extra ProxyPass calls
Merge pull request #1667 from cassiuschen/puma

Using Puma as Discourse's Webserver
Merge pull request #1464 from GarantiaData/single_redis_db

Support single redis DB.
Merge pull request #1788 from matsprea/patch-1

Update client.it.yml
FEATURE: added UI for tracking categories
BUGFIX: bundle exec migrations
FEATURE: add 2.1.0 as a target for testing
Update to latest version of rake