Fix indexing ConcreteEvaluation with AbstractRange

[jishnub]

Fixes

julia> Evaluation(JacobiWeight(0,0,Chebyshev()), 0.5)[1:4]
4-element Vector{Float64}:
  1.0
  0.5
 -0.5
 -1.0

[codecov[bot]]

Codecov Report

Patch coverage: 100.00% and no project coverage change.

Comparison is base (6f0cf81) 70.54% compared to head (85d2da8) 70.54%.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #488 +/- ## ======================================= Coverage 70.54% 70.54% ======================================= Files 81 81 Lines 8477 8478 +1 ======================================= + Hits 5980 5981 +1 Misses 2497 2497 ``` | [Impacted Files](https://app.codecov.io/gh/JuliaApproximation/ApproxFunBase.jl/pull/488?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=JuliaApproximation) | Coverage Δ | | |---|---|---| | [src/Operators/functionals/Evaluation.jl](https://app.codecov.io/gh/JuliaApproximation/ApproxFunBase.jl/pull/488?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=JuliaApproximation#diff-c3JjL09wZXJhdG9ycy9mdW5jdGlvbmFscy9FdmFsdWF0aW9uLmps) | `88.17% <100.00%> (+0.12%)` | :arrow_up: |

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