feat(runner): Buffer stdout and stderr for output when errors occur

[ghost]

When it is determined that an error occured during the run of a launch
it's useful to have output from the process.
We just need to know what was going on in order to debug (if necessary)

Related to #2663 Complete browser log output when process isn't started

Example output for a failing browser:

Achieved with

# Be in the project's root folder
folder=/tmp/karma-test
scriptName=faulty-browser.bash
script=$folder/$scriptName
mkdir -p $folder
echo '#!/usr/bin/env bash

echo "Starting..."
sleep 1
>&2 echo "An error was encountered"

exit 1
' > $script

chmod u+x $script

export PATH=$folder:$PATH
export CHROME_BIN=$scriptName
grunt test:client

[ghost]

Hmm... it looks like travis ran with Build#4019 with a non-existent commit da3702b 😕 Not sure what's going on.

I'll add a dummy commit to retrigger travis...

[dignifiedquire]

Thank you

[ghost]

Thanks for merging 😃