Use node 0.10 on Travis to avoid SSL error

Using npm with node 0.6 results in "SSL Error: CERT_UNTRUSTED":
https://travis-ci.org/madrobby/zepto/builds/16195932

See isaacs/npm#4379

.travis.yml

@@ -6,4 +6,4 @@ notifications:
     rooms:
       secure: VR6rWk0YhezBWnD8jPjSD8h/Q83S3NT0F34Au1vswt+/+Ku19S8X44vGVUG+NYdYyhg7uOqUaPN1Jr3KCpdcXgHEpUYiyBGJ8ebltavcjeHYWqK6ghcqgSnbDkifuC7Eu/9LcrOMOXgt+zkXjiVXW3+zyGVDcrs4cQ2vGY2DTYA=
 node_js:
-- 0.6
+- 0.10