Migration of iterators to Base, and sync with 0.4 syntax

[garborg]

Migration as of: JuliaLang/julia@7a8f434

[coveralls]

Coverage remained the same at 73.48% when pulling 822a5da on garborg:migration into 107ff7a on JuliaLang:master.

[garborg]

(Passed locally on master and release-0.3, with deprecation warnings in only the right places on both (groupby and sometimes count).)

[garborg]

Bump.

The one other bit of work I could see doing is deprecating count in favor of countfrom on 0.3 as well, but that could also come later.

[garborg]

Unless it would be better to move all the now-Base iterators completely out of here, to Compat. And have this just use Compat? That seems better to me.

[jiahao]

Let's have the test failure on 0.4 fixed and we can just merge it in without dawdling about where the code should go.

https://travis-ci.org/JuliaLang/Iterators.jl/jobs/50714323#L235

[coveralls]

Coverage increased (+6.71%) to 80.19% when pulling c93de58 on garborg:migration into 107ff7a on JuliaLang:master.

[coveralls]

Coverage increased (+13.74%) to 87.22% when pulling c93de58 on garborg:migration into 107ff7a on JuliaLang:master.