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
Merge tag 'v0.9.8'

version 0.9.8
Merge tag 'v0.9.8.1'

version 0.9.8.1
Delegate :username rather than using a class method.

This is just a little cleaner?
Topics Entered -> Topics Visited
whoops, I meant "Topics Viewed"
minor /top copyedit
another minor /top copyedit
BUGFIX: do not install dependencies from plugin, must be explicit
FEATURE: script/discourse import AND export
BUGFIX: export was broken, not exporting any tables
Merge tag 'v0.9.8.2'

version 0.9.8.2
BUGFIX: support nil params
fix for nil session in mobile_detection.rb
DIEEEE SOFTWARE.MD DIEEEEeeEE
FIXES #1833, thanks @stefanpenner
Trust Level 3: invited users start at default_invitee_trust_level + 1, unless default_invitee_trust_level is 2 or higher
In development mode, if an avatar is missing just serve up a placeholder
Renames `unboundDate` to `rawDate` because `date` is current unbound.