Error handler now returns a string instead (closes #10)

Commit hook now properly returns status code on failed formatting

.hooks/pre-commit

@@ -1,7 +1,10 @@
 #!/usr/bin/env bash
 
 # This hook lints the code, and if we're on develop or master, also forces the tests to pass.
-cargo fmt -- --check
+make lint &> /dev/null 2>&1 || {
+    >&2 echo "Format check failed, use 'make lint' for more information.";
+    exit 1;
+}
 
 branch=`git rev-parse --abbrev-ref HEAD`