Add membership ID to confirmation email
Checking membership level gets carried over if there's a form entry error
Added link to My Account if signed in
Removed duplicated 'Your details' legend and shifted help text for current password
Removed rogue <fieldset>
Put <section> tags aroud the main body

Closes #16
Merge pull request #18 from theodi/feature-15-emails

Added membership ID and general tidying up