Fix #87 failing test

[kschertler]

• Fixes failling doctest #87
• Replaces deprecated use of Base.download by using Downloads.download in flood_fill test to avoid a warning.

[kschertler]

Since I am not aware of an easy way to ensure that a doctest works if the output format has significantly changed over different Julia versions (like in the case of CartesianIndices), I have replaced the doctest by a repl documentation block - and added a simple normal test instead (e6d33a1).

The failed tests on Julia 1.0 are from unsatisfiable requirements detected for package DocStringExtensions, where I am not sure what to do about it.

[johnnychen94]

The failed tests on Julia 1.0 are from unsatisfiable requirements detected for package DocStringExtensions, where I am not sure what to do about it.

Since the majority of the community is shifting to Julia 1.6 compatibility, I think we can just drop the 1.0 tests. I believe only the really basic packages (such as OffsetArrays.jl) need to maintain 1.0 compatibility nowadays.

[johnnychen94]

Since I am not aware of an easy way to ensure that a doctest works if the output format has significantly changed over different Julia versions

My usual way is to limit the version that run doctest 😆

[kschertler]

Thanks @johnnychen94 for your explanations. Yes, this makes sense! Since you proposed to make Julia 1.6 the earliest supported version (and tests are OK for this version - as far as I see), I will close this PR and will create a new one for issue #89 that also shifts to 1.6 compatability.