Fix for rails mass-assignment protection

In rails 3.2.8, mass assignment can mean that the ActiveModel class
doesn't support mass assignment. This change ignores any such
protection and assumes it's your own data and you know what you're
doing with it.
Test for mass-assignment issue

Initial exploration seemed to point to a mass-assignment issue; this
change adds a test which attempts to reproduce the configuration that
rails is using when running the application that fails.
Merge branch 'mass-assignment' of https://github.com/jabley/data-anonymization

Merged the pull request from jabley
merged pull request from jabley with minor modification
updated thor gem dependency
updated thor gem dependency