New check: number of patches or bugs landed in nightly

[magopian]

Refs #196

Number of patches or bugs landed in nightly: can be queried from the mercurial pushlog using fromchangeand tochange (eg: https://hg.mozilla.org/mozilla-central/pushloghtml?fromchange=dd83069445a7&tochange=e7438140bb20).

The changesets could be taken from buildhub (eg https://github.com/mozilla/crash-clouseau/blob/master/crashclouseau/buildhub.py#L161). The commit messages could be parsed using https://github.com/mozilla/crash-clouseau/blob/master/crashclouseau/pushlog.py, and then a link to crash-clouseau could be built using https://github.com/mozilla/crashstop/blob/master/crashstop/patchinfo.py