Attempt to fix the composer install (#124)

* Attempt to fix the composer install

Composer isn't happy with installing HackTest, since that requires the HSL, which requires HackTest.
There must be some way of aliasing this that Fred referred to, but it appears it was already doing that.
Maybe we weren't specific enough?

#121 (comment)

> Still failing; I think this is the compsoer.json branch configuration - for example, we have this in master:
> 
> ```
> 	  "extra": {
>     "branch-alias": {
>       "dev-master": "4.x-dev"
>     }
>   },
> ```

* Add more guidance for composer

It needs to understand that this is the HSL HackTest is looking for.

composer.json

@@ -3,7 +3,8 @@
   "description": "The Hack Standard Library",
   "extra": {
     "branch-alias": {
-      "dev-master": "3.x-dev"
+      "dev-master": "3.30.x-dev",
+      "dev-v3.30.x": "3.30.x-dev"
     }
   },
   "license": "MIT",