Switch travis-ci to docker infrastructure

-stop manually downloading cmake

- increase the time limit here
- Have the tester print out the stderr when a test fails with the wrong exit code;
  this might make things spammy but I hope that it will be more helpful.
- Base EXTMODULE_DIR_PYSTON off the executable, not the tester
- modifying os.environ has no effect, even when spawning subprocesses...

Until I can figure out what the issue is that's making them fail.
(I don't feel great about removing tests, but I just added these a
few commits ago, so I think this makes the most sense for now.)

- generalize dynamic loading support
- copy include files to cmake build directory: we don't need it for our build,
  but we need them to be there for building extension modules
- some beginning hacks for supporting Cython

(increase the reopt and osr thresholds by 2x)

This helps django a ton.  will probably hurt our microbenchmarks
but I don't care much about those right now.

The issue is a difference between how PhiAnalysis and TypeAnalysis
handle OSR compilations: type analysis is osr-aware but phi analysis
isn't.  I think the right solution to this is to make phi and
definedness analysis also osr aware, but I want to get these other changes
in.

Set correct site-package directory, fix 'str * -1', add sys.dont_write_bytecode

Attach BoxedFile::gcHandler.

cmake explicitly list all c++ source files

Beginnings of a testsuite, starting with a simple django test.
Increases testing time by about 45 seconds which isn't great, but
tests a lot of stuff which is good.

We don't support arbitrary dict-like objects as the globals, but
in the special case that that dict-like object is just an attrwrapper
around the current module, we can fall back on our module-as-globals
support.

(Django 1.7.5)

We had a few callers but they weren't actually using the fact
that the strings were interned.

Implement misc stuff