Revert "Closes GH-85 Emit error rather than throwing."

This reverts commit f3d364122d.

Landed in master instead.

lib/fs.js

@@ -1027,8 +1027,7 @@ WriteStream.prototype.flush = function() {
 
 WriteStream.prototype.write = function(data) {
   if (!this.writable) {
-    this.emit("error", new Error('stream not writable'));
-    return false;
+    throw new Error('stream not writable');
   }
 
   this.drainable = true;

lib/tty_win32.js

@@ -99,8 +99,7 @@ WriteStream.prototype.isTTY = true;
 
 WriteStream.prototype.write = function(data, encoding) {
   if (!this.writable) {
-    this.emit("error", new Error('stream not writable'));
-    return false;
+    throw new Error('stream not writable');
   }
 
   if (Buffer.isBuffer(data)) {