Upgrade to Rust 1.31.0 (#2052)

* Upgrade to Rust 1.31.0
* Upgrade nightly
* Fix all clippy warnings
* Revert relaxed version check and update

src/fullnode.rs

@@ -51,7 +51,7 @@ impl LeaderServices {
         self.tpu.is_exited()
     }
 
-    pub fn exit(&self) -> () {
+    pub fn exit(&self) {
         self.tpu.exit();
     }
 }
@@ -63,7 +63,7 @@ pub struct ValidatorServices {
 
 impl ValidatorServices {
     fn new(tvu: Tvu, tpu_forwarder: TpuForwarder) -> Self {
-        ValidatorServices { tvu, tpu_forwarder }
+        Self { tvu, tpu_forwarder }
     }
 
     pub fn join(self) -> Result<Option<TvuReturnType>> {
@@ -76,7 +76,7 @@ impl ValidatorServices {
         self.tvu.is_exited()
     }
 
-    pub fn exit(&self) -> () {
+    pub fn exit(&self) {
         self.tvu.exit()
     }
 }
@@ -201,7 +201,7 @@ impl Fullnode {
     }
 
     /// Create a fullnode instance acting as a leader or validator.
-    #[cfg_attr(feature = "cargo-clippy", allow(too_many_arguments))]
+    #[allow(clippy::too_many_arguments)]
     pub fn new_with_bank(
         keypair: Arc<Keypair>,
         vote_account_keypair: Arc<Keypair>,
@@ -733,7 +733,8 @@ mod tests {
                     false,
                     None,
                 )
-            }).collect();
+            })
+            .collect();
 
         //each validator can exit in parallel to speed many sequential calls to `join`
         vals.iter().for_each(|v| v.exit());
@@ -1034,7 +1035,8 @@ mod tests {
                 ledger_initial_len,
                 last_id,
                 &tvu_address,
-            ).into_iter()
+            )
+            .into_iter()
             .rev()
             .collect();
             s_responder.send(msgs).expect("send");