doc: fix typos in cluster & errors

PR-URL: https://github.com/nodejs/node/pull/3011
Reviewed-By: Michaël Zasso <mic.besace@gmail.com>
Reviewed-By: Roman Reiss <me@silverwind.io>

doc/api/cluster.markdown

@@ -563,7 +563,7 @@ in the master process using the message system:
         console.log("numReqs =", numReqs);
       }, 1000);
 
-      // Count requestes
+      // Count requests
       function messageHandler(msg) {
         if (msg.cmd && msg.cmd == 'notifyRequest') {
           numReqs += 1;

doc/api/errors.markdown

@@ -308,7 +308,7 @@ An operation expected a file, but the given pathname was a directory.
 
 #### EMFILE: Too many open files in system
 
-Maxiumum number of [file descriptors](http://en.wikipedia.org/wiki/File_descriptor) allowable on the system has
+Maximum number of [file descriptors](http://en.wikipedia.org/wiki/File_descriptor) allowable on the system has
 been reached, and requests for another descriptor cannot be fulfilled until
 at least one has been closed.