Switched from using 'distutils' to 'setuptools' for installing AMBuild.

[WildCard65]

Fixes #68: See bpo-41282 for switch reason.

[dvander]

Thanks! I'll have to test this on our automated stuff, travis/appveyor install AMBuild from scratch each time, so there's potential for breakage. I should be able to do that soon.

[WildCard65]

@dvander I have tested the changes locally with pip set to verbose mode, fundamentally, I believe nothing should break (find_packages() even found all packages that were initially manually provided)

[dvander]

Okay, let's just merge this then and we can revert or fix in place if it breaks infrastructure.

[dvander]

This did break things, but it was simple enough to fix (the installation path of the "ambuild" script changed, I'm not sure what the new location is, but it's in PATH so I dropped the hardcoding).

[WildCard65]

@dvander The "ambuild" script became an executable on Windows, and what ever setuptools determines to be appropriate for Mac/Linux systems.