Allow interpolation with units!

[mbauman]

This patch allows InterpIrregular grids to be unitful (from SIUnits). InterpIrregular grids now accept Numbers for both creation and indexing. Because getindex is defined for Real on AbstractArrays, Grid needs to define both getindex(..., ::Real) and getindex(..., ::Number) to avoid ambiguity.

Here's what this allows:

julia> InterpIrregular([1.s,2.s,3.s], big([2.,3.,4.]), 0., InterpLinear)[1.5s:2.5s]
2-element Array{BigFloat,1}:
 2.5e+00
 3.5e+00

Of course, if you have a unitful grid, you must index it with compatible units.

[coveralls]

Coverage remained the same when pulling 06c4ff9182d3c49cbba0ac7c3e528cfdf9435405 on mbauman:siunits into ad2f1d79fcba47febd748bb6cf0364a3495d3364 on timholy:master.

[timholy]

Nice. In addition to SIUnits, this will make it easier to use DualNumbers when you want to check those derivatives.

The travis failure is odd: it seems to be trying to pull in Signals.jl, and that's what's failing. But I don't see anything in this that causes that behavior.

[mbauman]

Hah, pay no mind to that failure. That's the failure from a referenced commit within Signals.jl... which fails because it requires this patch. The Grid.jl tests passed just fine.

Great to hear this is more generally useful. I think it should be good to go.

[timholy]

Hah, I didn't even notice the context. No wonder I couldn't figure out where it was coming from.

[timholy]

Thanks again!

[mbauman]

Thanks!