Made path work for out-of-tree builds, added glfw for library name

Added glfw to names to search for GLFW_LIBRARY in the FindGLFW3 file,
because the shared library is named libglfw.so.3.0 and not found when
searching for libglfw3
Merge pull request #15 from dangets/cmake_mod_path

Made path work for out-of-tree builds, added glfw for library name