Avoid StackOverflow in view

[dlfivefifty]

In BlockArrays getindex may call view, so this redesigns getindex and view to both call _fill_getindex and avoid possible overflows.

[codecov]

Codecov Report

Merging #141 (19b7e25) into master (0606a8c) will not change coverage.
The diff coverage is 100.00%.

@@           Coverage Diff           @@
##           master     #141   +/-   ##
=======================================
  Coverage   95.66%   95.66%           
=======================================
  Files           4        4           
  Lines         531      531           
=======================================
  Hits          508      508           
  Misses         23       23           

Impacted Files	Coverage Δ
src/FillArrays.jl	94.27% <100.00%> (ø)

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