Includes the excluded slf4j-log4j12 dependency.
Allows user to pass a map of environment variables for NM process.
Now configuring executor's environment as per user specified env vars.

Also, configuring capsule to extract the JAR in work directory.
Added default environment variables.
Updated executor with correct launch command.
Merge branch 'phase1' of https://github.com/mesos/myriad into phase1