include overlay files in tar
Added the 'escript' command to the extended release script to permit
escripts to run in the release's environment without having to break
release encapsulation.

Example use:

$ _rel/myrelease/bin/myrelease escript priv/test.escript arg1 arg2 arg3

The argument to 'escript' is relative to the release's root.

The script is started with the 'escript' binary in the release's erts
release; has a current working directory of the release's root directory;
and additionally is started with visibility of an environment variable
called 'RELEASE_ROOT_DIR' which contains the absolute path of the
release's root directory.
Merge pull request #223 from tsloughter/tar

include overlay files in tar
provider task dependencies
add support for rebar3 deps dir
support config passed in as proplist instead of filename
fix tests for providers moved to new app and config list option
support only the 3 last major versions
Merge pull request #229 from Cloven/add_escript_command

Added the 'escript' command to the extended release script
Merge pull request #227 from tsloughter/master

Rebar3 support and code sharing
use long hostname if no hostname given
Merge pull request #231 from tsloughter/master

use long hostname if no hostname given