Explicitly add file and include directory for cython

Build under python3 apparently requires copying the vysmaw.pxd file to the build
directory, and passing -I. to cython when building cy_vysmaw. This is not the
case in python2.7...not really sure why that changed...but this patch also
appears to work for python2.7.

py/CMakeLists.txt

@@ -23,6 +23,8 @@ if("${isSystemDir}" STREQUAL "-1")
 endif("${isSystemDir}" STREQUAL "-1")
 
 find_package(Cython)
+set(CYTHON_FLAGS "-I.")
+configure_file(vysmaw.pxd vysmaw.pxd COPYONLY)
 add_cython_target(cy_vysmaw cy_vysmaw.pyx)
 
 include_directories(${PYTHON_INCLUDE_DIRS} ../src)