Fix watching of definition files

[jbrantly]

There was a discrepancy between the test runner and behavior when running webpack from the command line - if the previous bundle had the same hash as the current bundle in watch mode, webpack on the command line does not output any information (almost like nothing happened) whereas in the test runner we continued to operate as if something had been output. The first commit fixes that discrepancy.

Secondly, a change was made so that if a definition file is changed the hash for the compilation is also changed so that webpack does indeed output something to the screen. This reverts the changes to the declarationWatch test made in #100 and fixes #109.

Lastly, since the hashes have changed (and since hashes will now be different based on what your environment is since file paths are now included in the hashed data) the test runner has been updated to replace any hash in webpack output with [hash]. This allows the tests to run in any environment without issue.

cc @blakeembrey

[blakeembrey]

/\.d\.ts$/.test(filePath)?

[jbrantly]

Will change

[blakeembrey]

I think it's ok, mind explaining the this._module for me quickly (maybe again)?

[jbrantly]

Sure. this._module is the object that webpack uses to store info about the module (errors, etc). Most of the loader API operates on it under the hood (eg, addDependency, etc). In any case, there is a "meta" property that participates in the hash generation for the module. I use (abuse?) it here to make sure that webpack thinks the module is "new" (even though the actual output didn't change).

[jbrantly]

Updated based on code review, merging. Thanks!