Refactor process launching

[sos4nt]

I've refactored process launching to always use spawn, i.e. Process.spawn for Ruby 1.9 and POSIX::Spawn.spawn for Ruby 1.8 and JRuby.

Furthermore I've re-added support for PTY to address the missing output issue. Ruby doesn't buffer stdout when a tty is present. stdin on the other hand is closed to keep processes from expecting user input.

I've also removed foreman-runner since the tests are passing without it.

Let me know what you think.

[travisbot]

This pull request passes (merged 73fcf19 into 4a13122).

[dennisreimann]

+1 :)

[tysonmote]

+1

[ddollar]

Simulating a tty is convenient to work around things like stdout but it is still undesired because it makes your code in development run in a different mode than your code in production. You will need to have $stdout.sync = true in your app to run it under upstart or on Heroku also, so I'd rather not hide that fact from you in development.

Furthermore, PTY.spawn has a bug with Ruby 1.9.2 and some version of OSX (I think it was 10.6) that causes kernel panics when an unknown command is run.