directory structure change to work with glide

glide has its own requirements. My previous workaround caused me some
code checkin errors. Need to fix this.

weed/security/jwt.go

@@ -0,0 +1,72 @@
+package security
+
+import (
+	"net/http"
+	"strings"
+
+	"time"
+
+	"github.com/chrislusf/seaweedfs/weed/glog"
+	jwt "github.com/dgrijalva/jwt-go"
+)
+
+type EncodedJwt string
+type Secret string
+
+func GenJwt(secret Secret, fileId string) EncodedJwt {
+	if secret == "" {
+		return ""
+	}
+
+	t := jwt.New(jwt.GetSigningMethod("HS256"))
+	t.Claims["exp"] = time.Now().Unix() + 10
+	t.Claims["sub"] = fileId
+	encoded, e := t.SignedString(secret)
+	if e != nil {
+		glog.V(0).Infof("Failed to sign claims: %v", t.Claims)
+		return ""
+	}
+	return EncodedJwt(encoded)
+}
+
+func GetJwt(r *http.Request) EncodedJwt {
+
+	// Get token from query params
+	tokenStr := r.URL.Query().Get("jwt")
+
+	// Get token from authorization header
+	if tokenStr == "" {
+		bearer := r.Header.Get("Authorization")
+		if len(bearer) > 7 && strings.ToUpper(bearer[0:6]) == "BEARER" {
+			tokenStr = bearer[7:]
+		}
+	}
+
+	// Get token from cookie
+	if tokenStr == "" {
+		cookie, err := r.Cookie("jwt")
+		if err == nil {
+			tokenStr = cookie.Value
+		}
+	}
+
+	return EncodedJwt(tokenStr)
+}
+
+func EncodeJwt(secret Secret, claims map[string]interface{}) (EncodedJwt, error) {
+	if secret == "" {
+		return "", nil
+	}
+
+	t := jwt.New(jwt.GetSigningMethod("HS256"))
+	t.Claims = claims
+	encoded, e := t.SignedString(secret)
+	return EncodedJwt(encoded), e
+}
+
+func DecodeJwt(secret Secret, tokenString EncodedJwt) (token *jwt.Token, err error) {
+	// check exp, nbf
+	return jwt.Parse(string(tokenString), func(token *jwt.Token) (interface{}, error) {
+		return secret, nil
+	})
+}