No need to test *_FOUND variable before find_package call

From find_package documentation:
  Once one of the calls succeeds the result variable will
  be set and stored in the cache so that no call will search again.
Merge pull request #39 from ruslo/find_package

No need to test *_FOUND variable before find_package call
Reordered the arguments to uri::resolve #38.
Updated CMakeLists.txt to make sure that the build files are generated correctly from the cpp-netlib project.