Avoid using 'for in' to iterate over arrays.

'for in' also iterate over additionnal attributes set on the Array prototype, leading to unexpected
behaviors.
To make sigma.js more defensive against third-party libraries modifying the Array prototype, a more
classic way of iterating is required.

This patch solve issue #183.
PR #185 did not pass closureLint: Minor renaming

Just renamed max values in new "for" iterations to keep lines under 80 chars.