Support instant checkout button on product detail page

Add support for preset styles in settings.json

Swap uglifier for tersor so we can use newer javascript

Added new 'Powered by Big Cartel' badge

v1.0.4

A teeny release to pin BigDecimal to a ver that's needed because of our
Liquid library. Includes some minor README updates, too.

v1.0.3

Compass & Sass updates

Gets the latest Sass features possible given our version requirements.
This specifically allows:

```
.test
  color: red

  &__other
    color: blue
```

v1.0.2

- Fix issue with {{ pages.cart }}
- Update thin dependency for MacOS Big Sur

v1.0.1

Update new theme Contact template to use {{ contact.recaptcha }} instead
of the deprecated {{ contact.captcha }}

v1.0.0

Bumping to 1.0.0 to track major versions, spurred by a simple change of
adding ContactDrop#recaptcha to the API.

v0.12.3

Updates the JS API for the USD currency