An eye friendly color scheme

[sv2518]

Hi! I have added a new color scheme which I find slightly more eye friendly. I thought other users of Flamegraph might be interested too, so here is my PR. The colors are similar to the ones used in speedscope.app. The code is adapted from https://github.com/jlfwong/speedscope.

The color scheme can be accessed with --colors "eyefriendly"

Here is an example file

[brendangregg]

Thanks; I actually don't like these colors as it seems to reduce contrast and make it harder to read, but people have different tastes and I don't mind adding such things as options for people to choose. Can it also please be added to the usage message so that people can discover that it exists; here:

        --colors PALETTE # set color palette. choices are: hot (default), mem,
                         # io, wakeup, chain, java, js, perl, red, green, blue,
                         # aqua, yellow, purple, orange