Updates to waf-1.8.0
Now using the python tool rather than our homebaked stuff.
Updated README with info on homebrew libpython issue.
Disabled the clang build in travis.
Explicitly linking to libpython in boost configuration.
Re-enabled clang in travis config.
Added exception_translator class.
Added C++ analogs to Python's standard exceptions.
Added exception_info type.

This will replace the use of tuples for transporting exception info.
Added builtins() function for getting the builtins module.
Added exception_translator class.
Updated get_exception_info to use new exception_info class.
Removed erroneous config check for libboost_exception
Added documentation for exception_translator.
Using BOOST_FOREACH in exception_translator implementation.
Fixed documentation error.
Removed unnecessary include.
Removed unnecessary include.
Added some return value checks in translator tests.
Beefed up translator tests based on review feedback.