Merge pull request #688 from laughinghan/ci.imagemagick-install-failure

CI: imagemagick is actually pre-installed
diff --git a/circle.yml b/circle.yml
index 0a162f0..f93227b 100644
--- a/circle.yml
+++ b/circle.yml
@@ -35,9 +35,6 @@
   cache_directories:
     - ~/sauce-connect
   pre:
-    # imagemagick is installed to give us access to the
-    # `convert` tool to stitch together the screenshots.
-    - sudo apt-get update; sudo apt-get install imagemagick
     - "test $SAUCE_USERNAME && test $SAUCE_ACCESS_KEY
        # Sauce Labs credentials required. Sign up here: https://saucelabs.com/opensauce/"
     - ? |-