Check phantomjs's SHA-256 hash before installing

  This is probably overkill, but since we're supposed to be installing
  a specific version of this file, it seems worth checking to make
  sure we're getting the correct one.

Signed-off-by: David A. Wheeler <dwheeler@dwheeler.com>

circle.yml

@@ -1,7 +1,9 @@
 test:
   pre:
     - "[[ ! -s \"$(git rev-parse --git-dir)/shallow\" ]] || git fetch --unshallow"
-    - sudo curl --output /usr/local/bin/phantomjs https://s3.amazonaws.com/circle-downloads/phantomjs-2.1.1
+    - curl https://s3.amazonaws.com/circle-downloads/phantomjs-2.1.1
+    - sha256sum -c --strict --status phantomjs.sha256
+    - sudo mv phantomjs-2.1.1 /usr/local/bin/phantomjs/
   post:
     - bundle exec pronto run -f github text -c=$(git log --pretty=format:%H | tail -1) --exit-code
 deployment:

phantomjs.sha256

@@ -0,0 +1 @@
+4f63e6055c323b8657f0a546d4dd36afda5cd4e961c375f31b48d506a7c4296f  phantomjs-2.1.1