twister: Initialise Colorama during module load

This commit adds a call to the Colorama initialisation function during
the module execution so that ANSI color sequences are properly
converted to the relevant Win32 API calls on the Windows.

Note that the init function needs to be called per module, hence it is
also called in the `twisterlib.py`.

Signed-off-by: Stephanos Ioannidis <root@stephanos.io>