configuration changes

- nginx configured to allow larger uploads without buffering to disk (for large notebooks)
- notebook websocket protocol configurable
auto scaling improvements

- instances with older amis relinquish cluster leadership proactively
- improvements to auto-scaling logic
- also made ebs optional in mounting script
make curl available. fixes #157
Merge pull request #159 from tanmaykm/tanmaykm

auto scaling improvements, config tweaks, added curl
added Stan.jl. fixes #158
Merge pull request #160 from tanmaykm/tanmaykm

added Stan.jl. fixes #158
console color scheme selectable (default dark)

Console color scheme can be selected from a menu that appears with a right click.
Available schemes:
- Dark (dark background with light fonts) - default
- Light (light background with dark fonts)

Also needed https://github.com/tanmaykm/shellinabox_fork/commit/8d2a31df39e3097bcf5e56e6252372655233ca11
and https://github.com/tanmaykm/shellinabox_fork/commit/8e3a8c2943c97dea98621236cfbc7c20aedcccf7
Merge pull request #161 from tanmaykm/tanmaykm

console color scheme selectable (default dark)