Always flush message queue when tailing logs

Downsides: there is now a global variable for how long we buffer
messages. This *seems* nicer than having to pass it along, because we
need to construct a priority queue when the log repo is initialized (or
at least, we felt that we needed to).

[Finishes #70788884]
Add convenience script to run **some** packages
Document build process

[Finishes #70608194]
Simplify ui FailWithUsage method

It was absolutely absurd that we decided we needed to duplicate the
name of each command so that we could pass it to the UI object to
print usage. Maybe this change is only possible now because
codegangsta/cli updated its interface in the last few months, but
I'm still disappoint.

Yet another amazing perl find and replace.

[Finishes #70898678]
Bump version to 6.1.2