Merge pull request #247 from jandrieu/master

fixed content_type mistake in insertMultipart
diff --git a/lib/nano.js b/lib/nano.js
index f63a1ed..6d4b1e9 100644
--- a/lib/nano.js
+++ b/lib/nano.js
@@ -571,7 +571,7 @@
           follows: true,
           length: Buffer.isBuffer(att.data) ?
             att.data.length : Buffer.byteLength(att.data),
-          'content_type': att.contentType
+          'content_type': att.content_type
         };
         multipart.push({body: att.data});
       });