Add cursory readme and MIT license.

README.md

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+# Go Router
+
+```go
+type Router struct {
+    NotFoundHandler http.Handler
+}
+```
+
+## Setting path params
+
+Register routes with Router.AddRoute. Parts of the URI which start with a ":" are parameters. For example, if you registered `/user/:userID`, it would match `example.com/user/3`. You would then get a param called `userID` which would equal `"3"`.
+
+Inside the handler function you provide, access path parameters with the `PathParams` function.
+
+```go
+router.AddRoute(http.MethodGet, "user/:userID", func(w http.ResponseWriter, r *http.Request) {
+    params, _ := router.PathParams(requestMethod, requestPath)
+    
+    userID := params["userID"]
+})
+```
+
+## Not Found Handler
+
+If Router.NotFoundHandler is not a set, a default handler will be called when a route is not found. If you want to set your own handler, set Router.NotFoundHandler with the http.Handler you would prefer.