Make the example more functional with reusable filter functions

[DjebbZ]

The only real change in the reusable filter functions is that they check the parameter before accessing its length property. Otherwise it's "just functional sugar" (but the whole point of FP and FRP, right ? :D).

BTW, thanks for the plugin, I'm sure I'll use for my next (really first) Angular project.

[lauripiispanen]

Looks awesome! Just one thing I'm thinking: how about "shorterThan" and "longerThan" instead of "greaterThan" etc. We're looking at length here instead of plain comparison, right?

[DjebbZ]

I'm really a beginner in FP and FRP (learning Haskell these days...), but this is what I like with them : it makes semantics not only matter, but shine.