Fix queue_count metric documentation and setup

It was being initialized and deleted as `queue_counter` instead.

Author: britto

README.md

@@ -534,7 +534,7 @@ been started.
 |hackney.POOLNAME.no_socket    |counter  | Count of new connections                                             |
 |hackney.POOLNAME.in_use_count |histogram| How many connections from the pool are used                          |
 |hackney.POOLNAME.free_count   |histogram| Number of free sockets in the pool                                   |
-|hackney.POOLNAME.queue_counter|histogram| queued clients                                                       |
+|hackney.POOLNAME.queue_count  |histogram| queued clients                                                       |
 
 ## Contribute
 

doc/README.md

@@ -534,7 +534,7 @@ been started.
 |hackney.POOLNAME.no_socket    |counter  | Count of new connections                                             |
 |hackney.POOLNAME.in_use_count |histogram| How many connections from the pool are used                          |
 |hackney.POOLNAME.free_count   |histogram| Number of free sockets in the pool                                   |
-|hackney.POOLNAME.queue_counter|histogram| queued clients                                                       |
+|hackney.POOLNAME.queue_count  |histogram| queued clients                                                       |
 
 ## Contribute
 

doc/overview.edoc

@@ -529,7 +529,7 @@ been started.
 |hackney.POOLNAME.no_socket    |counter  | Count of new connections                                             |
 |hackney.POOLNAME.in_use_count |histogram| How many connections from the pool are used                          |
 |hackney.POOLNAME.free_count   |histogram| Number of free sockets in the pool                                   |
-|hackney.POOLNAME.queue_counter|histogram| queued clients                                                       |
+|hackney.POOLNAME.queue_count  |histogram| queued clients                                                       |
 
 ## Contribute
 

src/hackney_pool.erl

@@ -639,15 +639,15 @@ init_metrics(PoolName) ->
   _ = metrics:new(Engine, counter, [hackney_pool, PoolName, no_socket]),
   _ = metrics:new(Engine, histogram, [hackney_pool, PoolName, in_use_count]),
   _ = metrics:new(Engine, histogram, [hackney_pool, PoolName, free_count]),
-  _ = metrics:new(Engine, histogram, [hackney_pool, PoolName, queue_counter]),
+  _ = metrics:new(Engine, histogram, [hackney_pool, PoolName, queue_count]),
   Engine.
 
 delete_metrics(Engine, PoolName) ->
   _ = metrics:delete(Engine, [hackney_pool, PoolName, take_rate]),
   _ = metrics:delete(Engine, [hackney_pool, PoolName, no_socket]),
   _ = metrics:delete(Engine, [hackney_pool, PoolName, in_use_count]),
   _ = metrics:delete(Engine, [hackney_pool, PoolName, free_count]),
-  _ = metrics:delete(Engine, [hackney_pool, PoolName, queue_counter]),
+  _ = metrics:delete(Engine, [hackney_pool, PoolName, queue_count]),
   ok.