Reduce dependencies

[BraunreutherA]

There is a huge bulk of dependencies required - could be reduced, for example by asking the user for webpack or broserify and exclude the other one. This would decrease the installation time :)

[jskrzypek]

In general choosing not to generate some or any of the gulp tasks will cut down on the install time. You can also use the --skip-install flag when running the generator to not install any deps. Unfortunately the documentation of some of these options are kind of lost in the massive readme... That's something that needs working on :/

[thaiat]

i prefer the ability to switch between browsersify and webpack easily
I might take away a few seconds to reduce the dependencies but not much...

[thaiat]

see #269