Merge pull request #2 from KATT/master

Prevent `node-netpbm` from crashing on invalid JPEGs
Version 1.0.0
Merge pull request #3 from KATT/master

Don't execute pipeline if it exceeds the limit of active child processes
1.0.1 thanks to Alex / Ajax
Merge branch 'master' of github.com:punkave/node-netpbm
child process queue handled with async module

using async module as discussed in #5
version bump + changelog