Create PostAndCommentService, holds common methods

Some functionality such as saving, voting, deleting, etc. is common to
both posts and comments, so this service will hold such methods.

Tweaked the separate post/comment services accordingly. Fixed tests.

Signed-off-by: Vartan Benohanian <vartanbeno@gmail.com>

geddit.go

@@ -94,17 +94,17 @@ type Client struct {
 	// Reuse a single struct instead of allocating one for each service on the heap.
 	common service
 
-	Account    *AccountService
-	Comment    *CommentService
-	Flair      *FlairService
-	Listings   *ListingsService
-	Moderation *ModerationService
-	Multi      *MultiService
-	Post       *PostService
-	Search     *SearchService
-	Subreddit  *SubredditService
-	User       *UserService
-	Vote       *VoteService
+	Account        *AccountService
+	Comment        *CommentService
+	Flair          *FlairService
+	Listings       *ListingsService
+	Moderation     *ModerationService
+	Multi          *MultiService
+	Post           *PostService
+	PostAndComment *PostAndCommentService
+	Search         *SearchService
+	Subreddit      *SubredditService
+	User           *UserService
 
 	oauth2Transport *oauth2.Transport
 
@@ -138,10 +138,10 @@ func newClient(httpClient *http.Client) *Client {
 	c.Moderation = (*ModerationService)(&c.common)
 	c.Multi = (*MultiService)(&c.common)
 	c.Post = (*PostService)(&c.common)
+	c.PostAndComment = (*PostAndCommentService)(&c.common)
 	c.Search = (*SearchService)(&c.common)
 	c.Subreddit = (*SubredditService)(&c.common)
 	c.User = (*UserService)(&c.common)
-	c.Vote = (*VoteService)(&c.common)
 
 	return c
 }