Add simplecov to cucumber env

MSP-11647

Port simplecov setup from metasploit-version so that child processes, in
this case msfconsole, will load simplecov and report coverage back to
the parent process.  Coverage from msfconsole's cucumber features is the
only way to get coverage on portions of the command dispatcher commands.
Up aruba timeout for simplecov overhead

MSP-11647

Doubling the timeout is arbitrary, but travis-ci's limit for no output
is 10 minutes, so it can't go much higher.
Land #4256 after a rebase

Oops'ed the push.