Add develop task

Allow usage of mr.developer update feature by providing
a globally available handler

ade25/fabfiles/project/site.py

@@ -8,6 +8,13 @@ def update():
         run('nice git pull')
 
 
+@task
+def develop():
+    """ Update source packages """
+    with cd(env.code_root):
+        run('nice bin/develop up')
+
+
 @task
 def build():
     """ Buildout deployment profile (no update) """