Seed Breakpoints - v0.3.2

Fixes breakpoint-max / between mixins

The calculations were 1px off. If the breakpoint exists, the max width needs to be $max-width - 1px.

Bootstrap v4 breakpoint docs have some good examples of this:
http://v4-alpha.getbootstrap.com/layout/overview/#responsive-breakpoints

This issue was first spotted by @jaredmcdaniel

Note: This 1px offset only applies to breakpoints specified in $seed-breakpoints. If you pass in a custom number, it will use that number exactly.

---

Before:

// .scss
.class {
  @include breakpoint-max(md) {
    ...
  }
}

// .css
.class {
  @media (max-width: 768px) {
    ...
  }
}

After:

// .scss
.class {
  @include breakpoint-max(md) {
    ...
  }
}

// .css
.class {
  @media (max-width: 767px) {
    ...
  }
}