Update examples

  - for readability
  - for the new module structure of Uv
  - add build rules for examples
  - add structure for tests/ and build rule

Caveat
  - compilation does not work; types are incorrect (errno <-> int conversion)
wrong readme for installation
update compilation

  - fixed name conflict of object files in compilation
  - removed read2; does not exist in latest libuv
  - added back camluv_threadpool required for linking
  - removed unused import in camluv (now camluv_err).