Proposed score based cap

[bmaltais]

This change will allow users to specify a desired score to obtain using the new "ma" argument. For example -ma 0.04

If primitive reach this score before reaching the specified number of iterations (-n parameter) it will write the output and quit iterating.

This provides very consistent looking images independently of how many primitives and types required to obtain it.

[DictumMortuum]

I was just about to do this and create a pull request. Awesome!

[KarelPeeters]

Is there any chance you (@fogleman) will accept this pull request in the near future? This would be very useful for a project I'm working on. Would it be help you if I submit a new pull request that resolves this merge conflict?

[migueldemoura]

@flaghacker, you can use the fork from @bmaltais in the meantime.