Remove some unused #[derive] (#473)

We used to need them, probably when we were using Tera.

src/main.rs

@@ -30,8 +30,6 @@ extern crate rocket_i18n;
 extern crate scheduled_thread_pool;
 extern crate serde;
 #[macro_use]
-extern crate serde_derive;
-#[macro_use]
 extern crate serde_json;
 extern crate serde_qs;
 extern crate validator;

src/routes/blogs.rs

@@ -66,7 +66,7 @@ pub fn new_auth(i18n: I18n) -> Flash<Redirect>{
     )
 }
 
-#[derive(Default, FromForm, Validate, Serialize)]
+#[derive(Default, FromForm, Validate)]
 pub struct NewBlogForm {
     #[validate(custom(function = "valid_slug", message = "Invalid name"))]
     pub title: String,

src/routes/comments.rs

@@ -25,7 +25,7 @@ use plume_models::{
 use Worker;
 use routes::errors::ErrorPage;
 
-#[derive(Default, FromForm, Debug, Validate, Serialize)]
+#[derive(Default, FromForm, Debug, Validate)]
 pub struct NewCommentForm {
     pub responding_to: Option<i32>,
     #[validate(length(min = "1", message = "Your comment can't be empty"))]

src/routes/instance.rs

@@ -103,7 +103,7 @@ pub fn admin(conn: DbConn, admin: Admin, intl: I18n) -> Result<Ructe, ErrorPage>
     )))
 }
 
-#[derive(Clone, FromForm, Validate, Serialize)]
+#[derive(Clone, FromForm, Validate)]
 pub struct InstanceSettingsForm {
     #[validate(length(min = "1"))]
     pub name: String,

src/routes/posts.rs

@@ -272,7 +272,7 @@ pub fn update(blog: String, slug: String, user: User, cl: ContentLen, form: Leni
     }
 }
 
-#[derive(Default, FromForm, Validate, Serialize)]
+#[derive(Default, FromForm, Validate)]
 pub struct NewPostForm {
     #[validate(custom(function = "valid_slug", message = "Invalid title"))]
     pub title: String,

src/routes/session.rs

@@ -29,7 +29,7 @@ pub fn new(user: Option<User>, conn: DbConn, m: Option<String>, intl: I18n) -> R
     ))
 }
 
-#[derive(Default, FromForm, Validate, Serialize)]
+#[derive(Default, FromForm, Validate)]
 pub struct LoginForm {
     #[validate(length(min = "1", message = "We need an email or a username to identify you"))]
     pub email_or_name: String,

src/routes/user.rs

@@ -276,7 +276,7 @@ pub fn delete(name: String, conn: DbConn, user: User, mut cookies: Cookies, sear
     }
 }
 
-#[derive(Default, FromForm, Serialize, Validate)]
+#[derive(Default, FromForm, Validate)]
 #[validate(
     schema(
         function = "passwords_match",