Miscellaneous fixes/improvements

[colinxs]

As promised @oschulz, here's the PR! Everything should be non-breaking (I didn't break any tests at least). The only "questionable" change is 2a562cf which adds sizehint!/resize! where only the size in the last dimension is specified. Given that this is the only resizeable dimension it seems useful, but perhaps it would make more sense call them something different e.g. sizehintlastdim!/resizelastdim?

[colinxs]

Once this is reviewed/modified/approved I'll make the PR with broadcasting support :)

[codecov-io]

Codecov Report

Merging #20 into master will increase coverage by 0.02%.
The diff coverage is 97.43%.

@@            Coverage Diff             @@
##           master      #20      +/-   ##
==========================================
+ Coverage   89.83%   89.85%   +0.02%     
==========================================
  Files           3        3              
  Lines          59       69      +10     
==========================================
+ Hits           53       62       +9     
- Misses          6        7       +1     

Impacted Files	Coverage Δ
src/elasticarray.jl	89.39% <97.43%> (+0.10%)	⬆️

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[colinxs]

If you're wondering why I ditched _copyto_impl: the explicit version appeared to generate simpler LLVM code and it matched the style in Base.

[oschulz]

If you're wondering why I ditched _copyto_impl

Thanks for the explanation, I actually had wondered about that. :-)

[oschulz]

@colinxs , I'll wait for your PR with the broadcasting support before tagging a new release, Ok? Then we can decide whether it'll be v1.1 or v2.0.

[colinxs]

@oschulz sounds good!