Document "everything"

This is a good start but many things need to be documented better, but
this will at least allow us to turn on #[deny(missing_docs)]

src/entities/account.rs

@@ -82,6 +82,7 @@ fn string_or_bool<'de, D: Deserializer<'de>>(val: D) -> ::std::result::Result<bo
     })
 }
 
+/// Data structure used for updating user credentials
 #[derive(Debug)]
 pub struct CredentialsBuilder<'a> {
     display_name: Option<&'a str>,
@@ -91,6 +92,8 @@ pub struct CredentialsBuilder<'a> {
 }
 
 impl<'a> CredentialsBuilder<'a> {
+    /// Turns a `CredentialsForm` into a form suitable for PUTing to the
+    /// endpoint
     pub fn into_form(self) -> Result<Form> {
         let mut form = Form::new();
         macro_rules! add_to_form {

src/entities/list.rs

@@ -1,3 +1,4 @@
+/// Used for ser/de of list resources
 #[derive(Clone, Debug, Deserialize)]
 pub struct List {
     id: String,

src/entities/mention.rs

@@ -1,3 +1,4 @@
+/// Represents a `mention` used in a status
 #[derive(Debug, Clone)]
 pub struct Mention {
     /// URL of user's profile (can be remote)

src/entities/mod.rs

@@ -1,25 +1,37 @@
+/// Data structures for ser/de of account-related resources
 pub mod account;
+/// Data structures for ser/de of attachment-related resources
 pub mod attachment;
+/// Data structures for ser/de of card-related resources
 pub mod card;
+/// Data structures for ser/de of contetx-related resources
 pub mod context;
+/// Data structures for ser/de of instance-related resources
 pub mod instance;
 pub(crate) mod itemsiter;
+/// Data structures for ser/de of list-related resources
 pub mod list;
+/// Data structures for ser/de of mention-related resources
 pub mod mention;
+/// Data structures for ser/de of notification-related resources
 pub mod notification;
+/// Data structures for ser/de of relationship-related resources
 pub mod relationship;
+/// Data structures for ser/de of report-related resources
 pub mod report;
+/// Data structures for ser/de of search-related resources
 pub mod search_result;
+/// Data structures for ser/de of status-related resources
 pub mod status;
 
 /// An empty JSON object.
 #[derive(Deserialize, Debug, Copy, Clone, PartialEq)]
 pub struct Empty {}
 
+/// The purpose of this module is to alleviate imports of many common
+/// structs by adding a glob import to the top of mastodon heavy
+/// modules:
 pub mod prelude {
-    //! The purpose of this module is to alleviate imports of many common
-    //! structs by adding a glob import to the top of mastodon heavy
-    //! modules:
     pub use super::{
         account::{Account, CredentialsBuilder, Source},
         attachment::{Attachment, MediaType},