Update bitflags, other dependencies

Bitflags changed its macro codegen from creating constants to associated
constants on structs.

Upgrade path:

Update code from:

```rust
use serenity::model::permissions::{ADD_REACTIONS, MANAGE_MESSAGES};

foo(vec![ADD_REACTIONS, MANAGE_MESSAGES]);
```

to:

```rust
use serenity::model::Permissions;

foo(vec![Permissions::ADD_REACTIONS, Permissions::MANAGE_MESSAGES]);
```

1 files changed, 4 insertions, 4 deletions

diff --git a/src/model/invite.rs b/src/model/invite.rs
index 4c5aa28..ba7521a 100644
--- a/src/model/invite.rs
+++ b/src/model/invite.rs
@@ -2,7 +2,7 @@ use chrono::{DateTime, FixedOffset};
 use super::*;
 
 #[cfg(all(feature = "cache", feature = "model"))]
-use super::{permissions, utils as model_utils};
+use super::{Permissions, utils as model_utils};
 #[cfg(feature = "model")]
 use builder::CreateInvite;
 #[cfg(feature = "model")]
@@ -66,7 +66,7 @@ impl Invite {
 
         #[cfg(feature = "cache")]
         {
-            let req = permissions::CREATE_INVITE;
+            let req = Permissions::CREATE_INVITE;
 
             if !model_utils::user_has_perms(channel_id, req)? {
                 return Err(Error::Model(ModelError::InvalidPermissions(req)));
@@ -91,7 +91,7 @@ impl Invite {
     pub fn delete(&self) -> Result<Invite> {
         #[cfg(feature = "cache")]
         {
-            let req = permissions::MANAGE_GUILD;
+            let req = Permissions::MANAGE_GUILD;
 
             if !model_utils::user_has_perms(self.channel.id, req)? {
                 return Err(Error::Model(ModelError::InvalidPermissions(req)));
@@ -270,7 +270,7 @@ impl RichInvite {
     pub fn delete(&self) -> Result<Invite> {
         #[cfg(feature = "cache")]
         {
-            let req = permissions::MANAGE_GUILD;
+            let req = Permissions::MANAGE_GUILD;
 
             if !model_utils::user_has_perms(self.channel.id, req)? {
                 return Err(Error::Model(ModelError::InvalidPermissions(req)));