added :patrons_can_renew to app configs (modified)

Conflicts:
	app/models/app_config.rb
	app/views/app_configs/_form.erb
updated ability.rb with patron renewal option
updated reservation show page based on renewal ability
made items with zero-length max renewal ineligible for renewal (modified)

Conflicts:
	app/models/reservation.rb
Renamed configuration parameter to enable_renewals (modified)

Conflicts:
	app/views/app_configs/_form.erb
broadened restrictions to all roles except superuse
add enable_renewals to strong params
updated schema
made renewal redirect to reservation page w/ flash
deleted old renewal views / JS
updating Gemfile.lock for Travis (we need to fix our Gemfile)
updated specs to expect renewal to redirect to reservation show view
Merge branch 'master' into 916_renew_fix_master (Gemfile.lock conflict)

Conflicts:
	Gemfile.lock
Merge pull request #955 from YaleSTC/916_renew_fix_master

resolves #916