Provide a setting to flag if plugin options are updated after upgrading to v0.3.

Also fixes some erroneous use of double quotes where single quotes are suitable.

* Fix labels and IDs for both fields.
* Reorder fields.

Fixes a problem introduced in f3f435ba.

Use `Authy_WP::get_setting()` as the canonical source for plugin settings initialization.

Ensures that proper plugin settings are available when some are defined via constants in `wp-config.php`.

Tell browsers not to autocomplete the login token field since it's unlikely to ever receive a repeated value.

Introduce sanitization helper function for alphanumeric values and use said helper to sanitize values from constants introduced in 7577ba00. Fixes #12.

Also replaces existing API key sanitization with new helper function. Also corrects a hereto-undiscovered bug that caused a valid API key to be deemed invalid and cleared.

Introduce sanitization helper function for alphanumeric values and use said helper to sanitize values from constants introduced in r7577ba00. Fixes #12.

Also replaces existing API key sanitization with new helper function. Also corrects a hereto-undiscovered bug that caused a valid API key to be deemed invalid and cleared.

Check user's role before letting a sufficiently-priviledged user modify another user's Authy connection.

I hate myself for how I'm approaching this--see http://erick.me/15.

See #11.

* Improve non-JS experience

* Finish SMS Modal
* Remove debugging code errantly committed.

* Fix flawed logic in `send_sms()` method that prevented multiple attempts on failure.
* More PHPDoc

* Make common aspects of Ajax modals modular.
* Render basics of SMS modal window.

Also, random formatting changes and general cleanup.

* Basic API method for requesting an SMS.
* Setup method to check account for SMS support.

See #4.

Fixes #6.

Fixes #7.