Closes issue #79.

Use the public git url instead of the personal link

If Yara return error for `rules.match(data='string')` the Python wrapper
module crashes process with a segmentation fault.
Handle properly errors from 'data' and from 'pid'.

This Python function takes two optional kwargs: stack_size,
max_strings_per_rule. These each are unsigned int types and will be used
to update the YR_CONFIG_STACK_SIZE and YR_CONFIG_MAX_STRINGS_PER_RULE
configuration options in the matching engine, respectively. We found a
case preventing moving from cmdline yara to python-yara due to the lack
of control over these options in the Python module. This fixes that. I
suppose, at some point, it might be worthwhile to also implement a
get_config entrypoint as well.

Fix regression in "includes" argument in yara.compile. With includes=True includes were being disabled instead of enabled.

Closes #78.