Add State.input() for translating the state, then emiting an input event
Add State.translate.before_input and State.translate.before_display and invoke .befor_input in State.input
Add State.show(), which translates the state then invokes .display() (and fix .input to actually pass the user.i18n to .translate.before_input())
Change interaction machine to invoke State.show() instead of State.display()
Remove irrelevant docstring from State.show()
Change State.translate.before_input and .before_display to State.translators.before_input and .before_display
Merge branch 'feature/issue-134-translation-needs-to-happen-before-input-and-before-displaying-messages' into develop
Merge branch 'develop' of github.com:praekelt/vumi-jssandbox-toolkit into develop