Reject on Webpack compilation errors

[lzhoucs]

Type: bug fix

The following has been addressed in the PR:

• [x] There is a related issue
• [x] All code matches the style guide
• [x] Unit or Functional tests are included in the PR

Description:

This PR adds the logic to reject on compilation errors so subsequent dojo cli commands won't run. The same logic is used in Webpack cli code.

TypeScript compilation errors are exposed by Webpack through stats.compilation.errors which can be checked with stats.hasErrors().

Resolves https://github.com/dojo/cli-test-intern/issues/31

[kitsonk]

@matt-gadd we should either merge or close

[mwistrand]

I believe this was actually fixed with #208.

[kitsonk]

Closing as fixed by #208