feat(benchmark): add a simple benchmark for the di module

It adds the following tasks to the gulpfile:

1. `benchmarks/clean` // removes the compiled files
2. `benchmarks/build` // compiles all the files in `benchmarks` and creates a benchpress build
3. `benchmarks/run` // fires up a server

It also includes a very simple benchmark. It is not very useful and just serves as an example.

Extra notes:
1. Benchmarks run against the build folder. Right now everything is compiled with type checks enabled. We need to have another task (or maybe a flag) that compiles everything in production mode (without type checks).
Ah, I understand. Let's move the output of benchpress into `build/benchpress`. I really like having only one clean and serve task, and only one directory where stuff is being build...