Fix a compatibility issue with form_for as provided by other helper replacement gems.

Fixes #100
Add admin user tab translation

Related to spree/spree#3133
Use flash[:success], not flash.success

Fixes spree/spree#3166
Correct branch references to 2-0-stable for Spree components in Gemfile
Use currency in user order total.
correctly scoped translation key

Fixes #104
remove double quotes to match format of other strings

Related to #104
Add editing user spec.
Fix edit form.
add subject line and body specs for Spree::UserMailer

Fixes #106
Add default_url_options to user_mailer spec
Force Spree.user_class to be set to Spree::User to fix the infamous error:

rake aborted!
Association named 'spree_roles' was not found; perhaps you misspelled it?

It's tripped me up WAY too many times now.
Don't clear *all* the cookies and *all* the session when signing out
Update dependencies so we can build a rails 4 test env
Fix ActiveModel::ForbiddenAttributes errors

Down to 1 failing spec