Drop support for Go < 1.7: remove gorilla/context (#391)

* Drop support for Go < 1.7: remove gorilla/context
* Remove Go < 1.7 from Travis CI config
* Remove unneeded _native from context files

.travis.yml

@@ -3,8 +3,6 @@ sudo: false
 
 matrix:
   include:
-    - go: 1.5.x
-    - go: 1.6.x
     - go: 1.7.x
     - go: 1.8.x
     - go: 1.9.x

context.go

@@ -1,5 +1,3 @@
-// +build go1.7
-
 package mux
 
 import (

context_gorilla.go

@@ -1,26 +0,0 @@
-// +build !go1.7
-
-package mux
-
-import (
-	"net/http"
-
-	"github.com/gorilla/context"
-)
-
-func contextGet(r *http.Request, key interface{}) interface{} {
-	return context.Get(r, key)
-}
-
-func contextSet(r *http.Request, key, val interface{}) *http.Request {
-	if val == nil {
-		return r
-	}
-
-	context.Set(r, key, val)
-	return r
-}
-
-func contextClear(r *http.Request) {
-	context.Clear(r)
-}

context_gorilla_test.go

@@ -1,40 +0,0 @@
-// +build !go1.7
-
-package mux
-
-import (
-	"net/http"
-	"testing"
-
-	"github.com/gorilla/context"
-)
-
-// Tests that the context is cleared or not cleared properly depending on
-// the configuration of the router
-func TestKeepContext(t *testing.T) {
-	func1 := func(w http.ResponseWriter, r *http.Request) {}
-
-	r := NewRouter()
-	r.HandleFunc("/", func1).Name("func1")
-
-	req, _ := http.NewRequest("GET", "http://localhost/", nil)
-	context.Set(req, "t", 1)
-
-	res := new(http.ResponseWriter)
-	r.ServeHTTP(*res, req)
-
-	if _, ok := context.GetOk(req, "t"); ok {
-		t.Error("Context should have been cleared at end of request")
-	}
-
-	r.KeepContext = true
-
-	req, _ = http.NewRequest("GET", "http://localhost/", nil)
-	context.Set(req, "t", 1)
-
-	r.ServeHTTP(*res, req)
-	if _, ok := context.GetOk(req, "t"); !ok {
-		t.Error("Context should NOT have been cleared at end of request")
-	}
-
-}

context_test.go

@@ -1,5 +1,3 @@
-// +build go1.7
-
 package mux
 
 import (