Split stdout stderr for non-tty commands
Add stderr unit test
Make StdCopy works with huge amount of data
Add documentation
Update docs + fix endian issue
Merge pull request #1842 from dotcloud/split_stdout_stderr

* Runtime: Split stdout stderr
Add cross compilation to the standard build process

Currently, we will cross compile for Darwin (386, amd64) and Linux (386, amd64, and arm), but only because windows and freebsd currently won't compile without some tweaks to the docker source.
Updated Dockerfile to install FPM with "--no-rdoc --no-ri".