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
Dropping squashing commits from contribution process

 - Rephrases squashing of commits before submitting from a requirement to a recommendation
 - minor fixes around that
Update client.zh_TW.yml

Minor fixes for the chinese translations
Style 'urgent' composer popups differently

The two "bad behavior" composer popups get the 'urgent' class, which colors them red.
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
add btn-primary class to PM in usercard
Standardize on second person on preferences page
Update indexOf polyfill

Updated from the same source as the original comment. If IE8 isn’t
supported then this can be removed.
some incremental style enhancements, as discussed here https://meta.discourse.org/t/discourse-design-experiments/13479
Merge pull request #2079 from awesomerobot/master

some incremental style enhancements
Disabled editing of SSO overridden fields
Add JSHint to Travis validation

Run before the install as it acts as a fast fail vs the gem install time
Add jshintignore for failing files
JSHint: Add strict comparisons to poll_ui.js
update czech localization

Contributors: marmat, OukiDouki, Mirek2, zoul, MikulasDite
Hack for supporting pasting images into the composer in Firefox.
fixing mobile notificaiton badge