This patch adds support for runtime localization. A user may now provide a `locale` object (in the same shape as the locales in `/locale/*.json`) to `axe.configure()`.

For example:

```js
axe.configure({
  locale: {
    rules: {
      'some-rule': {
        help: 'the help message',
        description: 'the description'
      }
    },
    checks: {
      [...]
    }
  }
})
```

These locale strings are run thru `doT`, enabling template support. For example:

```js
axe.configure({
  locale: {
    rules: {
      foo: {
        help: 'some help',
        description: 'foo: {{~it.data:value}} {{=value}}{{~}}.'
      }
    },
    checks: {
      bar: {
        pass: 'the pass message',
        fail: 'something useful: {{~it.data:value}} {{=value}}{{~}}.'
      }
    }
  }
})
```

Upon calling `axe.reset()`, any custom locale will be reset to the "default" axe-core shipped with.