refactors context binding from _this to self
Merge pull request #1638 from velesin/i18n_helper_self_refactoring

refactors context binding from _this to self
FIX: in Rails 4, ActiveRecord::Base.descendants includes ActiveRecord::SchemaMigration for some reason. Exclude it from export.
Add an order for user_stats table in exporter
Minor typo fix in INSTALL-ubuntu.md.
Merge pull request #1641 from toolness/patch-1

Minor typo fix in INSTALL-ubuntu.md.
Refactor Users#upload_avatar method

Moved avatar file upload to ```AvatarUploadService``` class and
```AvatarUploadPolicy```

Address review comments + require missing file in spec
Merge pull request #1637 from railsaholic/refactor_users_upload_avatar_action

Refactor Users#upload_avatar method
Merge remote-tracking branch 'upstream/master'