Fix various issues

Fixes:

- Under Python 3.4, this happened whenever I did anything:

```
Traceback (most recent call last):
  File "../../fbuild-light", line 13, in <module>
    exec(compile(f.read(), fbuild_exename, 'exec'))
  File "../../bin/fbuild", line 159, in <module>
    sys.exit(main())
  File "../../bin/fbuild", line 135, in main
    result = build(ctx)
  File "../../bin/fbuild", line 82, in build
    target.function(ctx)
  File "/media/ryan/stuff/fb2/examples/c/fbuildroot.py", line 5, in build
    static = fbuild.builders.c.guess_static(ctx)
  File "../../lib/fbuild/builders/c/__init__.py", line 362, in guess_static
    ), *args, **kwargs)
  File "../../lib/fbuild/builders/c/__init__.py", line 325, in _guess_builder
    platform = fbuild.builders.platform.guess_platform(ctx, platform)
  File "../../lib/fbuild/db/__init__.py", line 121, in __call__
    result, srcs, dsts = self.call(*args, **kwargs)
  File "../../lib/fbuild/db/__init__.py", line 125, in call
    return ctx.db.call(self.function, ctx, *args, **kwargs)
  File "../../lib/fbuild/db/database.py", line 162, in call
    call_result = function(*args, **kwargs)
  File "../../lib/fbuild/builders/platform.py", line 72, in guess_platform
    stdout, stderr = ctx.execute((uname, '-s'), quieter=1)
  File "../../lib/fbuild/context.py", line 192, in execute
    stdout, stderr = p.communicate(input)
  File "/media/stuff/anaconda/lib/python3.4/subprocess.py", line 959, in communicate
    stdout, stderr = self._communicate(input, endtime, timeout)
  File "/media/stuff/anaconda/lib/python3.4/subprocess.py", line 1645, in _communicate
    self.wait(timeout=self._remaining_time(endtime))
  File "../../lib/fbuild/subprocess/killableprocess.py", line 225, in wait
    while time.time() < starttime + timeout - 0.01:
TypeError: unsupported operand type(s) for +: 'float' and 'NoneType'
```

- Some of the examples didn't work

- Use python3 instead of python3.1 in the hashbang at the top of several files.