Improves documentation (#13)

* Documents all env variables and adds an example project

* Adds godoc comments

* Fixed package naming issue

middleware/auth.go

@@ -6,8 +6,10 @@ import (
 	"net/http"
 )
 
+// UserIDKey is the key used to set and get the user id in the context of the current request
 const UserIDKey = "UserID"
 
+// Auth middleware redirects to /login and aborts the current request if there is no authenticated user
 func Auth() gin.HandlerFunc {
 	return func(c *gin.Context) {
 		_, exists := c.Get(UserIDKey)