fix(signup/login): improve visual styling and message display

I copied the signup and login forms pretty much verbatim from a sample Foundation form I found, but I was never truly happy with the way they looked. I cleaned them up so that things align better now, and it looks better both on desktop and mobile.
chore(sails): add config/local.js.example file

Sails by default ignores the config/local.js file, which is probably the right course of action, but there should probably be an example file if anybody other than me wants to work on developing this at some point.
fix(MainController): use the appName setting to define the page title programmatically

I should probably look for other places where we should similarly be using `sails.config` to reference global settings data, but this seemed like the most obvious need to start with.
feat(signup): add optional ReCAPTCHA to the signup form, with a custom responsive theme

The CAPTCHA is optional; details on how to add your API keys have been added to the README file. If you don't add your API keys either to `process.env` or config/local.js, then ReCAPTCHA won't be initialized and the signup form will display as it always has: without the CAPTCHA. Additionally, since ReCAPTCHA doesn't ship by default with a responsive widget, the display is customized to ensure it displays properly at small breakpoint.

Credit for the responsive widget goes to https://github.com/chrisvanpatten/responsive-recaptcha
Merge branch 'dev' of https://github.com/xiehan/sinead

Conflicts:
	package.json