Perf improvments from dev branch research.

While trying to improve perf on the dev branch, I found some general
speedups that were pretty easy to implement here.  Wow, nice
improvements!

lein test iris.perf-test
(216 cubes  no parallelism) : "Elapsed time: 2593.630651 msecs"
(216 cubes  2x parallelism) : "Elapsed time: 1324.937414 msecs"
(216 cubes  3x parallelism) : "Elapsed time: 921.86116 msecs"
(216 cubes  4x parallelism) : "Elapsed time: 992.562389 msecs"
(216 cubes  6x parallelism) : "Elapsed time: 991.780843 msecs"
(216 cubes  8x parallelism) : "Elapsed time: 910.661297 msecs"
(216 cubes 12x parallelism) : "Elapsed time: 1215.177516 msecs"
(216 cubes 16x parallelism) : "Elapsed time: 1352.760895 msecs"
(216 cubes 24x parallelism) : "Elapsed time: 1891.134987 msecs"
(216 cubes 32x parallelism) : "Elapsed time: 2668.556759 msecs"
(single fullscreen triangle  no parallelism) : "Elapsed time: 1599.242374 msecs"
(single fullscreen triangle  2x parallelism) : "Elapsed time: 925.452086 msecs"
(single fullscreen triangle  3x parallelism) : "Elapsed time: 1060.741359 msecs"
(single fullscreen triangle  4x parallelism) : "Elapsed time: 675.00857 msecs"
(single fullscreen triangle  6x parallelism) : "Elapsed time: 687.147944 msecs"
(single fullscreen triangle  8x parallelism) : "Elapsed time: 641.089701 msecs"
(single fullscreen triangle 12x parallelism) : "Elapsed time: 1342.737485 msecs"
(single fullscreen triangle 16x parallelism) : "Elapsed time: 927.358319 msecs"
(single fullscreen triangle 24x parallelism) : "Elapsed time: 1037.464765 msecs"
(single fullscreen triangle 32x parallelism) : "Elapsed time: 1330.315375 msecs"
perf fix things compiler cannot see

lein test iris.perf-test
(216 cubes  no parallelism) : "Elapsed time: 2459.377619 msecs"
(216 cubes  2x parallelism) : "Elapsed time: 1271.368485 msecs"
(216 cubes  3x parallelism) : "Elapsed time: 872.008159 msecs"
(216 cubes  4x parallelism) : "Elapsed time: 891.478095 msecs"
(216 cubes  6x parallelism) : "Elapsed time: 968.881487 msecs"
(216 cubes  8x parallelism) : "Elapsed time: 1176.386881 msecs"
(216 cubes 12x parallelism) : "Elapsed time: 1354.854667 msecs"
(216 cubes 16x parallelism) : "Elapsed time: 1478.763259 msecs"
(216 cubes 24x parallelism) : "Elapsed time: 2101.085249 msecs"
(216 cubes 32x parallelism) : "Elapsed time: 2675.92429 msecs"
(single fullscreen triangle  no parallelism) : "Elapsed time: 1434.428697 msecs"
(single fullscreen triangle  2x parallelism) : "Elapsed time: 776.432289 msecs"
(single fullscreen triangle  3x parallelism) : "Elapsed time: 681.848307 msecs"
(single fullscreen triangle  4x parallelism) : "Elapsed time: 630.480751 msecs"
(single fullscreen triangle  6x parallelism) : "Elapsed time: 554.966573 msecs"
(single fullscreen triangle  8x parallelism) : "Elapsed time: 664.827979 msecs"
(single fullscreen triangle 12x parallelism) : "Elapsed time: 807.22114 msecs"
(single fullscreen triangle 16x parallelism) : "Elapsed time: 745.126423 msecs"
(single fullscreen triangle 24x parallelism) : "Elapsed time: 940.865884 msecs"
(single fullscreen triangle 32x parallelism) : "Elapsed time: 1149.552544 msecs"