Setup Documenter

[tkf]

This PR sets up Documenter. I leave out deploydocs setup so you still need to do the usual Travis setup.

I'm sending this PR because it would motivate me to write docstring next time I send a feature PR :)

[codecov-io]

Codecov Report

Merging #34 into master will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master      #34   +/-   ##
=======================================
  Coverage   56.61%   56.61%           
=======================================
  Files          15       15           
  Lines         952      952           
=======================================
  Hits          539      539           
  Misses        413      413

Impacted Files	Coverage Δ
src/LazyArrays.jl	100% <ø> (ø)	⬆️

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[dlfivefifty]

Unfortunately I don't have time to work on docs right now, but I've added you as a collaborator so feel free to merge whatever you feel doesn't require a review.

Note that it might be worth waiting to the code settles down a bit more. For example:

#35
#33

and also I'm thinking that BroadcastArray and ApplyArray should not wrap a Broadcasted and Applied instance, instead have the same fields (and so make dispatch a bit simpler).

[tkf]

I've added you as a collaborator

Thanks!

I don't think that's enough access to setup Travis/Documenter. It's not urgent at all, but can you do it when you have time #36?

BroadcastArray and ApplyArray should not wrap a Broadcasted and Applied instance, instead have the same fields

I think it makes sense.