Fixing some errors in README, fixes #15

[theanalyst]

• README.md: The following fixes are done
  • Fixed small bug which mentioned M-x inferior-lisp
  • note added for Windows users where defaults may not work Also added the following:
  • Installation instructions added for MELPA

[berkerpeksag]

Thanks! :) https://github.com/hylang/hy-mode/commit/4d06d9df27cabbdcdfe13f9217a703cb78a99be0