Add space value for border-image-repeat

[toptalo]

When I was try to find bug for issue CSSLint/csslint#718, I notice that not all valid properties for border-image-repeat are described. So I added space. Also I added tests for border-image-repeat.

They all passed:

✔ 'initial' is a valid value for 'border-image-repeat'
✔ 'inherit' is a valid value for 'border-image-repeat'
✔ 'unset' is a valid value for 'border-image-repeat'
✔ 'stretch' is a valid value for 'border-image-repeat'
✔ 'round stretch' is a valid value for 'border-image-repeat'
✔ 'foo' is an invalid value for 'border-image-repeat'
✔ 'round stretch foo' is an invalid value for 'border-image-repeat'

So parser-lib is not under suspicion =)

[stubbornella]

LGTM

[stubbornella]

Thanks for adding tests!

[frvge]

LGTM

[toptalo]

Thanks!