Attempt at converting settings page to a form with editable username and email
Fixed hacky form layout
Fixed user info in header not being vertically centred in Firefox (not sure why display: table-cell was needed, but removing it appears to have no other effects)
Fixed form validation being one keystroke behind the user’s input, by listening for the `oninput` event instead (which is more elegant and is supported by the latest versions of all major browsers)
Cleaned up CSS for settings page, fixed a couple browser-specific bugs, and marked both email and username as being required fields (so that validation can function correctly)
Implemented logic to submit profile settings changes, which also updates local storage, reloads the page, and notifies the user on success
Style fixes, better error logging, cleaned up HTML markup on input fields
Removed a reference to `$this` upon successfully updating the user’s profile that would be destroyed after reloading the page (it wasn’t needed anyway)
Fixed settings input fields being stuck to a fixed width - now scales to fit available space up to a reasonable max width
Disabled editing of email address
Added a global "filters" module (in shared/filters.js) for nunjucks filters that neither nunjucks nor commonplace provide, and added a safeurl filter there to add escaping slashes where needed
Removed filters.js and just added the safeurl filter to commonplace's helpers.js instead
Moved safeurl filter yet again, this time to main.js
Style fix
Now with more style
Merge pull request #41 from cvan/editable-settings

Added ability to edit username and email address