Add Logging to stdout

[asedarski]

NOT MVP!

Add logging to Explore for better understanding of what may go wrong.

Use the monolog service provider built into silex:
http://silex.sensiolabs.org/doc/providers/monolog.html

For reference, this is how to log to stdout with monolog: http://www.lornajane.net/posts/2014/logging-to-stdout-with-monolog