Added Member Tags API calls

I added two API calls.
 - GET: /lists/{list_id}/members/{subscriber_hash}/tags
 - POST: /lists/{list_id}/members/{subscriber_hash}/tags

API doc: https://mailchimp.com/developer/reference/lists/list-members/list-member-tags/

go.sum

@@ -0,0 +1,10 @@
+github.com/davecgh/go-spew v1.1.0 h1:ZDRjVQ15GmhC3fiQ8ni8+OwkZQO4DARzQgrnXU1Liz8=
+github.com/davecgh/go-spew v1.1.0/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
+github.com/pmezard/go-difflib v1.0.0 h1:4DBwDE0NGyQoBHbLQYPwSUPoCMWR5BEzIk/f1lZbAQM=
+github.com/pmezard/go-difflib v1.0.0/go.mod h1:iKH77koFhYxTK1pcRnkKkqfTogsbg7gZNVY4sRDYZ/4=
+github.com/stretchr/objx v0.1.0/go.mod h1:HFkY916IF+rwdDfMAkV7OtwuqBVzrE8GR6GFx+wExME=
+github.com/stretchr/testify v1.5.1 h1:nOGnQDM7FYENwehXlg/kFVnos3rEvtKTjRvOWSzb6H4=
+github.com/stretchr/testify v1.5.1/go.mod h1:5W2xD1RspED5o8YsWQXVCued0rvSQ+mT+I5cxcmMvtA=
+gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405/go.mod h1:Co6ibVJAznAaIkqp8huTwlJQCZ016jof/cbN4VW5Yz0=
+gopkg.in/yaml.v2 v2.2.2 h1:ZCJp+EgiOT7lHqUV2J862kp8Qj64Jo6az82+3Td9dZw=
+gopkg.in/yaml.v2 v2.2.2/go.mod h1:hI93XBmqTisBFMUTm0b8Fm+jr3Dg1NNxqwp+5A1VGuI=

members.go

@@ -14,6 +14,8 @@ const (
 
 	member_notes_path       = single_member_path + "/notes"
 	single_member_note_path = member_notes_path + "/%s"
+
+	member_tags_path = single_member_path + "/tags"
 )
 
 type ListOfMembers struct {
@@ -116,8 +118,9 @@ type MemberNoteShort struct {
 }
 
 type MemberTag struct {
-	ID   int    `json:"id"`
-	Name string `json:"name"`
+	ID        int    `json:"id"`
+	Name      string `json:"name"`
+	DateAdded string `json:"date_added"`
 }
 
 func (list ListResponse) GetMembers(params *InterestCategoriesQueryParams) (*ListOfMembers, error) {
@@ -344,3 +347,44 @@ func (mem Member) DeleteNote(id string) (bool, error) {
 	endpoint := fmt.Sprintf(single_member_note_path, mem.ListID, mem.ID, id)
 	return mem.api.RequestOk("DELETE", endpoint)
 }
+
+// ------------------------------------------------------------------------------------------------
+// Tags
+// ------------------------------------------------------------------------------------------------
+
+type ListOfMemberTags struct {
+	baseList
+
+	Tags []MemberTag `json:"tags"`
+}
+
+type ListOfTagsRequest struct {
+	Tags      []TagsRequest `json:"tags"`
+	IsSyncing bool          `json:"is_syncing"`
+}
+
+type TagsRequest struct {
+	Name   string `json:"name"`
+	Status string `json:"status"`
+}
+
+func (mem Member) GetTags(params *BasicQueryParams) (*ListOfMemberTags, error) {
+	if err := mem.CanMakeRequest(); err != nil {
+		return nil, err
+	}
+
+	endpoint := fmt.Sprintf(member_tags_path, mem.ListID, mem.ID)
+	response := new(ListOfMemberTags)
+
+	return response, mem.api.Request("GET", endpoint, params, nil, response)
+}
+
+func (mem Member) CreateTags(body *ListOfTagsRequest) error {
+	if err := mem.CanMakeRequest(); err != nil {
+		return err
+	}
+
+	endpoint := fmt.Sprintf(member_tags_path, mem.ListID, mem.ID)
+
+	return mem.api.Request("POST", endpoint, nil, body, nil)
+}