Disable closespider_itemcount by default

This setting is mainly used for demo purposes. And it seems to be
highly confusing for a wide audience. We decided to disable it by
default, so crawly will not stop suddenly.

README.md

@@ -69,7 +69,6 @@ historical archival.
    config :crawly,
      closespider_timeout: 10,
      concurrent_requests_per_domain: 8,
-     closespider_itemcount: 1000,
      middlewares: [
        Crawly.Middlewares.DomainFilter,
        Crawly.Middlewares.UniqueRequest,

documentation/configuration.md

@@ -93,11 +93,11 @@ config :crawly,
 
 Defines a list of middlewares responsible for pre-processing requests. If any of the requests from the `Crawly.Spider` is not passing the middleware, it's dropped.
 
-### closespider_itemcount :: pos_integer()
+### closespider_itemcount :: pos_integer() | :disabled
 
-default: 5000
+default: :disabled
 
-An integer which specifies a number of items. If the spider scrapes more than that amount and those items are passed by the item pipeline, the spider will be closed. If set to nil the spider will not be stopped.
+An integer which specifies a number of items. If the spider scrapes more than that amount and those items are passed by the item pipeline, the spider will be closed. If set to :disabled the spider will not be stopped.
 
 ### closespider_timeout :: pos_integer()
 

documentation/quickstart.md

@@ -58,7 +58,6 @@ Goals:
    config :crawly,
      closespider_timeout: 10,
      concurrent_requests_per_domain: 8,
-     closespider_itemcount: 1000,
      middlewares: [
        Crawly.Middlewares.DomainFilter,
        {Crawly.Middlewares.RequestOptions, [timeout: 30_000]},

lib/crawly/manager.ex

@@ -85,7 +85,10 @@ defmodule Crawly.Manager do
     delta = items_count - state.prev_scraped_cnt
     Logger.info("Current crawl speed is: #{delta} items/min")
 
-    case Application.get_env(:crawly, :closespider_itemcount, 1000) do
+    case Application.get_env(:crawly, :closespider_itemcount, :disabled) do
+      :disabled ->
+        :ignored
+
       cnt when cnt < items_count ->
         Logger.info(
           "Stopping #{inspect(state.name)}, closespider_itemcount achieved"