Dutch translation updated

Up til commit dd400bb
Refactored post model to reduce duplication in validator methods
Show Inbox before Sent Items
Improve style of security tab of category modal
Require rspec-rails in Gemfile to fix 'spec' task
Merge pull request #857 from chrishunt/chrishunt/fix-spec-rake-task

Require rspec-rails in Gemfile to fix 'spec' task
Merge pull request #850 from bplexico/refactor_post_rb

Refactored post model to reduce duplication in validator methods
Merge pull request #855 from sanderdatema/dutch_translation

Dutch translation updated
Revert "Require rspec-rails in Gemfile to fix 'spec' task"

This reverts commit c6c223d1c9f47d756a08e8064b30e987751f72cd.
Add explicit 'spec' rake tasks

This doesn't require auto-loading of rspec-rails and puts the 'spec'
task in the rake task list (rake -T)
Merge pull request #858 from chrishunt/chrishunt/create-explicit-spec-task

Create 'spec' rake task
Update DEVELOPER-ADVANCED.md
add YAML lint hint to the top of lang YAML files
DRY up the user model slightly

regular? is just the inverse of staff?
Clean up update_visit_record!

update_visit_record! appears to add user_visit record if one
doesn't exist and days_visited is simply a counter for the number
of visit records.
simplify spam flag reason text
Added a spec for staff? and regular?
Fix for topic excerpt being from the wrong post
Set created_at manually through PostCreator
Show posts for last page when page out of range