A few spelling fixes.

Thanks Bjarki. Closes GH-561.

doc/api/buffers.markdown

@@ -43,7 +43,7 @@ Allocates a new buffer containing the given `str`.
 
 Writes `string` to the buffer at `offset` using the given encoding. Returns
 number of octets written.  If `buffer` did not contain enough space to fit
-the entire string it will write a partial amount of the string. In the case
+the entire string, it will write a partial amount of the string. In the case
 of `'utf8'` encoding, the method will not write partial characters.
 
 Example: write a utf8 string into a buffer, then print it

doc/api/events.markdown

@@ -8,7 +8,7 @@ You can access this module by doing: `require("events");`
 Typically, event names are represented by a camel-cased string, however,
 there aren't any strict restrictions on that, as any string will be accepted.
 
-Functions can be then be attached to objects, to be executed when an event
+Functions can then be attached to objects, to be executed when an event
 is emitted. These functions are called _listeners_.
 
 

doc/api/modules.markdown

@@ -43,7 +43,7 @@ object.  (Alternatively, one can use `this` instead of `exports`.) Variables
 local to the module will be private. In this example the variable `PI` is
 private to `circle.js`. The function `puts()` comes from the module `'util'`,
 which is a built-in module. Modules which are not prefixed by `'./'` are
-built-in module--more about this later.
+built-in modules--more about this later.
 
 ### Module Resolving
 
@@ -76,7 +76,7 @@ Additionally node will search for directories called `node_modules` starting
 at the current directory (of the module calling `require`) and upwards
 towards the root of the package tree.
 This feature makes it easy to have different module versions for different
-environments. Imagine the situation where you have a devopment environment
+environments. Imagine the situation where you have a development environment
 and a production environment each with a different version of the `foo`
 module: `projects/x/development/node_modules/foo` and
 `projects/x/production/node_modules/foo`.

doc/api/streams.markdown

@@ -33,7 +33,7 @@ Emitted if there was an error receiving data.
 
 `function () { }`
 
-Emitted when the underlying file descriptor has be closed. Not all streams
+Emitted when the underlying file descriptor has been closed. Not all streams
 will emit this.  (For example, an incoming HTTP request will not emit
 `'close'`.)