Introduction

Simple implementation of the hangman game using TDD

Features
- Should pick a random word from the dictionary at =/usr/share/dict/words= (sudo apt-get install dictionaries-common if you don't have this file). The word should have atleast 6 characters.
- The user should be prompted to enter a letter. At each turn the following information should be presented.
  1. The word masked with _ for unguessed letters and the actual letter for guessed letters.
  2. The number of remaining turns (You will start with 8 turns)
  3. The letters which have been guessed already (correct and wrong)
- If the user enters a letter that was already guessed, just say so and repeat the turn (don't update anything).
- If the user enters a correct letter, update the masked word, the list of guessed letters and go the next turn
- If the user enters a wrong letter, reduce the number of remaining turns, update the list of guessed letters and go to the next turn
- If the user successfully guesses the word before 8 wrong turns, print "Congratulations!" and quit.
- If the user does not guess the word before 8 wrong turns, print "You failed. The secret word was ..." and exit.
e.g

Suppose the secret word is elephant, the transcript might be like this
```
  The secret word is : --------
  You have 8 turns left
  Letters guessed : 
  What is your guess? 
```

Suppose the user types x

  Sorry 'x' is not there in the word
  The secret word is : --------
  You have 7 turns left
  Letters guessed : x
  What is your guess?

Suppose the user types e

  'e' is there in the word
  The secret word is : e-e-----
  You have 7 turns left
  Letters gussed : e x
  What is your guess?

Suppose the user types x again

  You have already guessed 'x'
  The secret word is : e-e-----
  You have 7 turns left
  Letters guessed : e x
  What is your guess?

And so on till the end.