Update Install Documentation (Version Numbers)

[ax3l]

Updates a couple of links and version numbers in the install documentation:

• OpenMPI 1.5.1+ including GPU-aware link Disable mpi_leave_pinned for non-GPU-aware MPIs #438
• boost 1.56/1.57 support since Close #588 Boost 1.56.0+ and Aliases #593
• update link to new official pngwriter repo on GitHub

[PrometheusPi]

@ax3l Who should be assigned to this pull request?

[ax3l]

I left it open for the first maintainer that feels competent about catching it via self-assignment :)
Are you the one, Neo?

[PrometheusPi]

I get an Access Denied error with this URL.

[PrometheusPi]

http:// instead of https:// works fine

[ax3l]

I was suprised by that some days ago, too and wrote that to nvidia.

I will change the link to http:// in the mean time, I thought the complete webpage is down :)
Update: no does not make sense, the site uses https in internal links again. I will contact the support. Pls merge at the meantime and don't worry.

[PrometheusPi]

OK.