Try not running a full meteor --get-ready before Circle CI tests.

In the ongoing struggle with Circle CI-specific test failures, the
preparatory `meteor --get-ready` has been a consistent point of failure,
before any real tests have the chance to run.

Using a lighter-weight command (meteor --help) that still does most of
what --get-ready did seems worth a try, though it might just defer
memory-intensive work until later, so we'll have to see what happens.

circle.yml

@@ -13,9 +13,9 @@ dependencies:
     - ".meteor"
     - ".babel-cache"
   override:
-    # shouldn't take longer than 10 minutes
-    - ./meteor --get-ready:
-        timeout: 600
+    # shouldn't take longer than 5 minutes
+    - ./meteor --help:
+        timeout: 300
         environment:
           METEOR_PRETTY_OUTPUT: 0
           METEOR_DISABLE_OPTIMISTIC_CACHING: 1