systemd socket activation
after socket activation remove LISTEN_FDS and LISTEN_PID environment variables
Update README for shorter gem description

Hoe parses out the `## Description` section for use in the gemspec description,
which at present is very large and uses markdown that the gemspec / rubygems
doesn't care about.

This commit replaces the description with an abbreviated version, and puts the
full description below a new header "built for speed and concurrency"
Add some documentation for Clustered mode

- use `-w`
- tune with `-C` config file and `on_worker_boot`
a little more or Thread use with Clustered mode
Fix typo
fix: stop leaking sockets on restart (affects ruby 1.9.3 or before)
Update puma-manager.conf

Added quotes to /etc/puma.conf
It is 2013 [ci skip]
Merge pull request #269 from joneslee85/patch-8

It is 2013 [ci skip]
Merge pull request #267 from baruchlubinsky/master

Fix an error in puma-manager.conf
Merge pull request #259 from sugitak/fix_socket_leak

fix: stop leaking sockets on restart (affects ruby 1.9.3 or before)
Merge pull request #247 from catsby/update_gem_description

Shorten the gemspec description
Merge pull request #231 from urbaniak/socket-activation

Socket activation
Error out early if there is no app configured
Ignore errors on the cross-thread pipe. Fixes #246

The @notify pipe is used to give commands to the server running in
another thread. The server might be shutting down at the moment we send
it a command, thus it might have closed @notify, so we ignore errors.
Handle errors from the server better
Handle all read exceptions properly. Fixes #252
Fix typo
Handle ConnectionError rather than the lowlevel exceptions