alpha rarefaction plots take uneven time when plotting in parallel

[antgonza]

On #25 we found an odd behavior when plotting on parallel stderr and stddev: one is taking longer than the other and we do not know why? We need to figure out if this is a problem with qiime, expected behavior or something else.

[ElDeveloper]

@antgonza Do you think this might be solved by biocore/qiime#667 or is there more profiling left to do?

[antgonza]

I just tested it and it doesn't fix this issue; maybe is an Apache
configuration problem.