Also print certain exec() errors
Add optimization flag to cut down on binary size

Trusty was generating code almost double the size of before the last
commit.  Not sure why exactly.  Telling GCC not to add async unwind
tables got it back down to size.  It shouldn't affect anything outside
of debugging anyway.  Minit is pretty simple... if you have to debug it,
something went drastically wrong.
Back down debhelper version so it builds on lucid
Add Dockerfile for building a minit base image
Update example for chazomaticus/minit base images
Update docs