subprocess for c++ v0.4.0

Changes:

• CTRL_BREAK_EVENT is sent for SIGTERM & terminate() functions on windows.
• fixed invalid handles when launching a python script that then launches new
  processes.
• new kIsWin32 constant to help avoid ifdef use.
• Documentation wording to be more confident as the library is looking pretty
  good, and I haven't felt like changing much of the API.