ns/as-alias not supported

Zdar, this code breaks dirac:

```clojure
(ns a.b.c "Test" (:require [bm-web.routes :as-alias routes]))
```

The `as-alias` syntax allows to refer to `:bm-web.routes` by `::routes` (instead of it refering to `:MY-CURRENT-NS/routes`). It's a fairly new CLJ addition.

However dirac isn't happy about it:

```
#ExceptionInfo{:message nil,
:data {:clojure.error/source nil,
:clojure.error/line nil,
:clojure.error/column nil,
:clojure.error/phase :compilation},
:cause #ExceptionInfo{:message "Only :as, :refer and :rename options supported in :require / :require-macros; offending spec: [bm-web.routes :as-alias routes]",
:data {:tag :cljs/analysis-error}}}
```

It shows `Internal Dirac Error [D:implant:70] "Unable to parse namespace from source\n"` in the devtools.