v5.0.0

[major] Removed deprecated & dead code
[-] Render404 was removed. This can be easily replaced using Render function
[-] middleware package was removed. There are now sub packages for individual middleware functions, middleware/cors, middleware/accesslogs
[-] cleaned up all unit tests
[-] updated travis config to use correct version in tests
[-] updated minimum test version of Go to 1.13 to support errors.Is