Review Email design

[TBSliver]

The wording and layout of the two (currently at least) emails which are sent out to customers probably need looking at for design and layout. These are here:

https://github.com/Pear-Trading/Registration/blob/master/templates/email/forgotten_password.html

https://github.com/Pear-Trading/Registration/blob/master/templates/email/new_user.html

These will need the same colour scheme and items added to them as #20 comes up with, but will need to be included in the files themselves due to email specialness.