List `markdown-mode' as a dependency

This should fix the Travis build

1 files changed, 1 insertions, 0 deletions

diff --git a/Cask b/Cask
index 3e939ef..f0c70fb 100644
--- a/Cask
+++ b/Cask
@@ -8,6 +8,7 @@
 (depends-on "json" "1.4")
 (depends-on "url")
 (depends-on "cl-lib")
+(depends-on "markdown-mode")
 
 (development
  (depends-on "ert"))