Use the latest Steal minor branch

This upgrades us to the latest Steal minor branch which had a couple of bug fixes that shouldn't cause any problems.
Merge pull request #106 from bitovi/latest-minor

Use the latest Steal minor branch
Upgrade to latest transpile

This updates us to use the latest transpile from the minor branch.
Merge pull request #107 from bitovi/latest-transpile

Upgrade to latest transpile
Reset window.define before evaling in pluginify

Our System.define shim needs to have the same logic as our AMD shim.
That is, before executing code remove our `window.define` and replace it
with the original version, and then set back to our version after the
eval. This causes problems with "bad AMD". That is AMD that has it's
define statement at the bottom and therefore must be marked as a global.
Fixes #73
Merge pull request #108 from bitovi/system-eval

Reset window.define before evaling in pluginify
Show file size of bundles in verbose mode

If verbose mode is enabled, output the file size as part of writing out
the bundles. Fixes #56
Merge pull request #109 from bitovi/bundle-sizes

Show file size of bundles in verbose mode
Only include Traceur runtime if used

This changes, based on the new version of Traceur, to only include the
runtime if the source is using the runtime. Because the runtime no
longer uses the `assertObject` calls it used to, for simple scenarios
such as only importing/exporting the runtime is not needed. This changes
`has_es6` to instead of testing the format, test for the presence of
`$traceurRuntime` in the source. Fixes #75 and #99