bugfix for compass-installed?

catch the (previously uncaught) exception when there isn't a `compass`
binary on the `$PATH`, return `false` instead

src/cryogen_core/sass.clj

@@ -17,7 +17,10 @@
 (defn compass-installed?
   "Checks for the installation of Compass."
   []
-   (= 0 (:exit (sh "compass" "--version"))))
+  (try
+    (= 0 (:exit (sh "compass" "--version")))
+    (catch java.io.IOException _
+      false)))
 
 (defn find-sass-files
   "Given a Diretory, gets files, Filtered to those having scss or sass