fix(build): add ambient type definitions

[mgechev]

1. Update to TypeScript (1.9 has fix for TS4020).
2. Update ts-node and typings.
3. Add ambient type definitions for CacheStorage, CacheOptions, Cache.
4. Add ambient type definitions for jshashes.
5. Remove useless require from gulpfile.ts.
6. Add merge-stream in order to merge both js and dts streams of
   gulp-typescript.
7. Publish typings field in package.json.
8. Remove inline Promise interface definition and take the one from
   es6-shim typings.

Note that the Cache interfaces does not completely align to the standard.

[jeffbcross]

Awesome, are you planning to update the build process to emit dist/worker.d.ts as part of this PR?

[mgechev]

Yes, sure. What do you think about the standard compatibility? Should we keep the definitions as they are, or to make align to the API in the link?

[jeffbcross]

Personally, I see the typings as a stop gap until Cache typings are included in TypeScript. I don't think they need to be complete.

[mgechev]

@jeffbcross everything from #15 should be here.

All merge conflicts are resolved and the PR is squashed.

[mgechev]

Need to rebase. I'll do that when I land.

[mgechev]

@jeffbcross, we have green build. I incorporated #27 here and added a few more enhancements on top.

I edited the commit message above with all the changes. The big diff comes from the removed node_modules directory.

Let me know if you prefer the two commits squashed into a single one.