Don't lint pseudo-selectors in SelectorFormat

The SelectorFormat linter shouldn't lint pseudo-selectors since these
must always use a hyphenated lowercase convention.

Change-Id: I1b3f65a8017d69c5f984b7721f626c9c27348e75
Reviewed-on: http://gerrit.causes.com/44887
Tested-by: jenkins <jenkins@brigade.com>
Reviewed-by: Shane da Silva <shane.dasilva@brigade.com>