Typo fix to the programming guide in the docs

Typo fix to the programming guide in the docs. Changed the word "distibuted" to "distributed".

Author: Cesar Arevalo <cesar@zephyrhealthinc.com>

Closes #1495 from cesararevalo/master and squashes the following commits:

0c2e3a7 [Cesar Arevalo] Typo fix to the programming guide in the docs

docs/programming-guide.md

@@ -739,7 +739,7 @@ def doStuff(self, rdd):
 
 While most Spark operations work on RDDs containing any type of objects, a few special operations are
 only available on RDDs of key-value pairs.
-The most common ones are distibuted "shuffle" operations, such as grouping or aggregating the elements
+The most common ones are distributed "shuffle" operations, such as grouping or aggregating the elements
 by a key.
 
 In Scala, these operations are automatically available on RDDs containing
@@ -773,7 +773,7 @@ documentation](http://docs.oracle.com/javase/7/docs/api/java/lang/Object.html#ha
 
 While most Spark operations work on RDDs containing any type of objects, a few special operations are
 only available on RDDs of key-value pairs.
-The most common ones are distibuted "shuffle" operations, such as grouping or aggregating the elements
+The most common ones are distributed "shuffle" operations, such as grouping or aggregating the elements
 by a key.
 
 In Java, key-value pairs are represented using the 
@@ -810,7 +810,7 @@ documentation](http://docs.oracle.com/javase/7/docs/api/java/lang/Object.html#ha
 
 While most Spark operations work on RDDs containing any type of objects, a few special operations are
 only available on RDDs of key-value pairs.
-The most common ones are distibuted "shuffle" operations, such as grouping or aggregating the elements
+The most common ones are distributed "shuffle" operations, such as grouping or aggregating the elements
 by a key.
 
 In Python, these operations work on RDDs containing built-in Python tuples such as `(1, 2)`.