Text Input Form Styles

Base form styles for:

```css
input[type="email"]
input[type="number"]
input[type="password"]
input[type="search"]
input[type="tel"]
input[type="text"]
input[type="url"]

input[type="color"]
input[type="date"]
input[type="datetime"]
input[type="datetime-local"]
input[type="month"]
input[type="time"]
input[type="week"]
```

Includes some SASS helpers (adapted from [bourbon](https://github.com/thoughtbot/bourbon/blob/master/app/assets/stylesheets/addons/_html5-input-types.scss)) to avoid type repetition.