[#345] update rails & other gems
[#345] update gems
Merge branch 'master' into 345-update_to_rails4

Conflicts:
	Gemfile
	Gemfile.lock
[#345] remove observers; use new labmda syntax
[#345] move lib/modules/models to app/models/concerns; small refactoring
[#345] move markdown to helper
[#345] fix mistype
[#345] fix url_for
[#345] fix Sass::SyntaxError - File to import not found or unreadable
[#345] remove assets group from the Gemfile; fix compass-rails version
[#345] downgrade jquery-rails version because Sprockets::FileNotFound - couldn't find file 'jquery-ui'
[#345] fix mistypes
[#345] avoid lazy load because
ActiveRecord::StatementInvalid - PG::ProtocolViolation: ERROR:  bind message supplies 4 parameters,
but prepared statement "a7" requires 2
[#345] remove deprecations with association conditions
[#345] small refactoring
[#345] try fix PG::UndefinedObject: ERROR:  type "hstore" does not exist
[#345] remove a deprecated option
[#345] fix activity concern
[#345] fix No such middleware to insert after: Rack::Lock (RuntimeError)
[#345] remove an unnecessary line