First draft of the introduction

Rewrote the introduction as a usecase.

Pulled the introduction into a separate file.

This is a first draft but thought I'd get out a general idea of the introduction I had out as soon as possible.
"There are a great many reasons to still physically hand over a phone, such as letting someone take part in a phone call, letting them play a game, and view vacation photographs."
I don't like how you sometimes split sentences, but this is a personal preference.