set default role in users_controller#create
explicitly deny non admins/superusers the ability to change view mode
added view mode reset validator in user model
set default view mode in schema to 'normal' and updated schema (v3.4)

Conflicts:
	db/schema.rb
updated schema for only v3.4 migrations (forgot to drop db before last commit
fixed controller method to not use strong params from v4.0
Merge branch 'release-v3.4' into 966_admin_permissions_34
updated changelog w/ #966
fixed indentation of 2nd case statement in ability.rb
Merge branch 'release-v3.4' into 966_admin_permissions_34
resolved merge conflict in CHANGELOG.md

Conflicts:
	CHANGELOG.md
Merge pull request #971 from YaleSTC/966_admin_permissions_34

resolves #966 for v3.4