Update from TSD to typings

[demurgos]

Hi,
This PR updates the definition files management from TSD to typings and fixes #436.

The build instructions were updated to include typings install after npm install.

I could successfully build gulp-typescript and was I able to remove the warning I got as a consumer (tsd.d.ts not found), but I'd still be careful with this PR to ensure that it does not introduce any breaking changes.

[demurgos]

Hi,
I know that this is a change in the build process so it requires some time to review it. Do you need more details ? I would gladly help you clarify and test any potential issues.

I have some dependent packages that throw errors because of #436 and I hoped to solve it quickly.

[ivogabe]

Sorry for the late reply, I didn't have time to look at this earlier. I also looked at your types branch, and got that working after two changes. You accidentally included both types and typings, so all libraries were declared twice. The tests would also pick up the @types files, which broke several tests. I explicitly excluded the @types files and now all tests pass again. Can you take a look at #448 and see whether that works for you?

[demurgos]

Ok, I'll check that, looks like you are right: I forgot to completely remove typings.

[demurgos]

I am closing this PR in favor of #448.