Change conveyor_bins to use the http url so that readonly access works

.gitmodules

@@ -1,6 +1,6 @@
 [submodule "submodule/conveyor_bins"]
 	path = submodule/conveyor_bins
-	url = git@github.com:makerbot/conveyor_bins.git
+	url = http://github.com/makerbot/conveyor_bins.git
 [submodule "submodule/mw-scons-tools"]
 	path = submodule/mw-scons-tools
 	url = https://github.com/makerbot/mw-scons-tools.git