Use new lyricwiki url.

  Hi febuiles, I found your emacs extension really cool! I'm new to git and github and found in this project a great  opportunity to start contributing. 
  
  Please let me know what you think about the changes. I'm looking forward to continue contributing to your project. Thanks!
Changes in this topic branch: 
1. Updated the code to use the new lyricwiki url.
2. Put regular expressions into constant values, to make the code more readable, also to make it easier to debug in case that the html format changes.
3. Added the song title to the beginning of the buffer, and set the lyrics buffer in view-mode so the user can rapidly exit using `q'.