Default to starting a single process

[nvllsvm]

What
Start a single process unless explicitly configured to start more.

sprockets.http/sprockets/http/runner.py

Line 61 in 7991f99

def start_server(self, port_number, number_of_procs=0):

Current
Virtual-CPU-number of processes are started.
1 process is started when running in debug mode.

Why
It's more consistent when deploying to environments where one is not responsible for provisioning the underlying system (ex. Docker).

[nvllsvm]

It's important to use a single process when running a sprockets.http with envconsul. Otherwise, each reload of envconsul will result in lingering child processes.

hashicorp/envconsul#177

[nvllsvm]

Just saw that this is a thing: tornadoweb/tornado#2801

I'm now thinking of removing this option entirely from sprockets.http and always using only a single process.

@dave-shawley Thoughts?