Display error if no anagrams found

Add handling empty array code to word_list.erb, e.g. if there are no
anagrams, word_list.erb displays message saying that there are no
anagrams.
First step to to making finding anagrams faster

Added sorted words column to database.  Anagrams are found by sorting
the characters in the word into alphabetical order. Presorting the
words in the dictionary will make it faster to find anagrams.

Additionally, the sorted words column is an index. This makes finding
the anagrams a log(n) operation instead of an (n) operation.
ripping out debugging statements
Extract find anagrams algorthim into Word class method

To make the code more readable (and reusable), move anagram-finding
logic from controller index.rb the Words model.  It fits better as
a method than as a pile of logic hanging out in a post controller.