Add missing timestamps to the 'members' table
Merge branch 'members_table_timestamps' into 'master'

Add missing timestamps to the 'members' table

In 20140914145549_migrate_to_new_members_model.rb we forgot to set the
created_at and updated_at times for new records in the 'members' table. This
became a problem after commit c8e78d972a5a628870eefca0f2ccea0199c55bda which
was added in GitLab 7.5. With this migration we ensure that all rows in
'members' have at least some created_at and updated_at timestamp.

See merge request !1272