add instructions for setting up MongoDB on C9.io

seed/challenges/03-back-end-development-certification/mongodb.json

@@ -17,8 +17,9 @@
         "Click the \"Create workspace\" button.",
         "Once C9 builds and loads your workspace, you should see a terminal window in the lower right hand corner. In this window use the following commands. You don't need to know what these mean at this point.",
         "Install <code>learnyoumongo</code> with this command: <code>npm install learnyoumongo -g</code>",
+        "Set up your mongod alias by following the directions at <a href='https://community.c9.io/t/setting-up-mongodb/1717' target='_blank'>https://community.c9.io/t/setting-up-mongodb/1717</a>.",
         "Now start the tutorial by running <code>learnyoumongo</code>.",
-        "Whenever you run a command that includes <code>mongod</code> on c9.io, be sure to also use the <code>--nojournal</code> flag, like this: <code>mongod --nojournal</code>.",
+        "Whenever you run a command that includes <code>mongod</code> on c9.io, use <code>./mongod</code> instead.",
         "Note that you can resize the c9.io's windows by dragging their borders.",
         "Make sure that you are always in your project's \"workspace\" directory. You can always navigate back to this directory by running this command: <code>cd ~/workspace</code>.",
         "You can view this Node School module's source code on GitHub at <a href='https://github.com/evanlucas/learnyoumongo'>https://github.com/evanlucas/learnyoumongo</a>.",