CuVec v2.5.0 beta

• add SWIG support via cuvec.i (#7)
• add & document example_swig
• improve & document example_mod
• fix external #includes
  • multiple definitions
  • missing cuda runtime header
  • use of static & templates
  • namespace clashes
• statically link CUDA libraries
• use macros to reduce code duplication
• add and fix tests
• add performance checks
• misc code tidy