add dev version (#1886)

* add dev version

* Update version.go

* Update version.go

README.md

@@ -119,10 +119,6 @@ $ curl https://raw.githubusercontent.com/gin-gonic/examples/master/basic/main.go
 $ go run main.go
 ```
 
-## Prerequisite
-
-Now Gin requires Go 1.8 or later and Go 1.10 will be required next major version.
-
 ## Quick start
  
 ```sh

version.go

@@ -5,4 +5,4 @@
 package gin
 
 // Version is the current gin framework's version.
-const Version = "v1.4.0"
+const Version = "v1.4.0-dev"