Supporting darwin/macports

setup.py of v0.4.0 forces the talib include and lib dir to /usr/local/include and /usr/local/lib. MacPorts installs files to /opt/local, so the compiler can never find the headers and libs. This change checks if /opt/local/include/ta-lib exists and uses /opt/local/... instead of /usr/local/... If this does not exist, /usr/local/... is taken by default.

Can you release a new version to pypi with these changes? Thank you!