linear scale in heatmap renders very light heatmap

[mrjones-plip]

when you change weightByAttributeScale to linear instead of log the resulting map is so light as to almost be useless.

steps to reproduce:

1. change examples/heatmap.html maptable project to have weightByAttributeScale = 'linear'
2. load up examples/heatmap.html in a browser

expected: map renders heatmap with a linear fall off
actual: map renders heatmap with an almost imperceptible amount of color on the heatmap

[mrjones-plip]

oh yeah! This may be working as designed and it just needs larger initial values. We're using it on this map for reference https://office.pch.net/ixpdir-maptable/heatmap.html

[melalj]

@Ths2-9Y-LqJt6 Can you close this issue then?

[mrjones-plip]

ok, so when testing this on master after merging #56 to master that changing weightByAttributeScale still has imperceptible affects. even tweaking the function in weightByAttribute didn't really change the affect. So, while I said this may not be an issue, I still think it is.

my test set up was ./examples/heatmap.html