doc: typo fixes

doc/api/buffer.markdown

@@ -35,7 +35,7 @@ encoding method.  Here are the different string encodings.
   should be avoided in favor of `Buffer` objects where possible. This encoding
   will be removed in future versions of Node.
 
-* `'hex'` - Encode each byte as two hexidecimal characters.
+* `'hex'` - Encode each byte as two hexadecimal characters.
 
 ## Class: Buffer
 

doc/api/http.markdown

@@ -543,7 +543,7 @@ Example:
 In node 0.5.3+ there is a new implementation of the HTTP Agent which is used
 for pooling sockets used in HTTP client requests.
 
-Previously, a single agent instance help the pool for single host+port. The
+Previously, a single agent instance helped pool for a single host+port. The
 current implementation now holds sockets for any number of hosts.
 
 The current HTTP Agent also defaults client requests to using

doc/api/readline.markdown

@@ -77,7 +77,7 @@ Once you have a readline instance, you most commonly listen for the
 `"line"` event.
 
 If `terminal` is `true` for this instance then the `output` stream will get
-the best compatability if it defines an `output.columns` property, and fires
+the best compatibility if it defines an `output.columns` property, and fires
 a `"resize"` event on the `output` if/when the columns ever change
 (`process.stdout` does this automatically when it is a TTY).
 

doc/api/vm.markdown

@@ -95,7 +95,7 @@ Example: compile and execute code in a existing context.
     // { animal: 'cat', count: 3, name: 'CATT' }
 
 Note that `createContext` will perform a shallow clone of the supplied sandbox object in order to
-initialise the global object of the freshly constructed context.
+initialize the global object of the freshly constructed context.
 
 Note that running untrusted code is a tricky business requiring great care.  To prevent accidental
 global variable leakage, `vm.runInContext` is quite useful, but safely running untrusted code