Add charts for merged v closed and community v us

Prior to this commit, the data did not display how many of the closed
pull requests were actually merged, or whether or not the submitter
was a Puppet Labs employee. Now there are two pie charts which show
the ratio of merged:closed and community:puppet labs.
Add check to avoid bad pull requests

Prior to this commit, there were issues with certain pull requests
because the user that opened them had deleted their account. This meant
that the needed data could not be retrieved and written to the database.

Now, there is a check before the call to write to the database is made
to ensure the needed fields are not null. If they are, it skips entry
of that pull request and prints a warning message.