choose pre-compiled version of ionic css

[gruppjo]

Introduce an option for the user when setting up the project that provides the user either with a precompiled version of the ionic css or one that is compiled with every styles gulp task (as it is now).

This could greatly reduce the sass compile time for many use-cases. See #3 (comment)

[MathiasTim]

I just tried out this feature, its cool. But there is something which bothers me.
Why is the 'css-way' recommended? I cannot agree there. Of course its faster, but you loose the ability to change any color/variable of ionic and we do this a lot!

So I think we should do this:

❯ ionic SASS (more flexible)
 ionic CSS (faster) 

[gruppjo]

I thought that most people would probably use ionic 'as is'. What do you think? However I'm totally open to changing it.

[gruppjo]

change:

> ionic CSS (faster, for beginners)
ionic SASS (more flexible, for pros)