renamed User#report_levels to User#available_levels, and tweaked it to include return value of User#next_level
Merge branch 'master' into level_select
Revert "renamed User#report_levels to User#available_levels, and tweaked it to include return value of User#next_level"

This reverts commit 5643824cf9bf18b9101066a24b33d50dc5e7b499.
added a more attractive level-selection feature for the Users#show page