Dutch translation updated

Up til commit dd400bb
Refactored post model to reduce duplication in validator methods
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
Fix spelling mistake in spec doc