Fix all the things

[andyferris]

Solve various inference issues. Replaces #495 and #330.
Closes #493.

Note: the eltype of empty arrays may become Union{} in
map, broadcast, and mapreduce(...; dims = Val{N}).

[andyferris]

Since there seems to be little enough harm in Union{} eltypes for statically sized arrays that have passed through map or broadcast, and that lets us remove all references to inference, I decided to try that for now.

[coveralls]

Coverage decreased (-0.008%) to 94.985% when pulling 03165ba on ajf/noinference into 81dd6ca on master.

[andyferris]

I will go ahead and merge this. Please comment here or open issues with whatever the fallout is :)

[c42f]

Wow great to see all the things fixed! Time to close all the those tiresome issues and release version 1.0.0 :-)

[andyferris]

Lol.

By the time I was done, it seemed to annoying to enumerate all the little things... :)

But actually yes, I would like to release v1.0 soon. (I think we should deprecate FixedSizeArrays and Immutable arrays first, though).

[c42f]

Agreed, those old interfaces should go. If there's any remaining difference in functionality we should subsume that and move on.