chore(): add explicit usage of filter in demo
chore(directive): use the service instead of the filter within directive
feat(service): add $translate.instant() for instant translations

the api of `$translate.instant()` is the same `$translate()` except not returning a promise and being not deferred
feat(filter): filter now use $translate.instant() since promises could not use
Merge pull request #337 from knalli/feature/translate-instant

Feature/translate instant