Implement notifications

Update README.md and change notifications text

Write more comments in Miyuki#track!

Fix "can't convert nil to String" while looking for watchDir in configuration

Add support for 0.2-version configuration files, add notes and advices in README

[BROKEN] adding a notifier factory for cross-platform notification

TerminalNotify is OSX-only, and I'm using Linux, so I'm including libnotify for notifications

Fix previous commit.

I was experiencing a strange error. Investigating, I had two different versions of Miyuki (two Miyukis... www): uninstalling them and rebuilding/reinstalling only 0.3 version (this one!) did the trick.

Don't notify if already downloaded

I'm sorry, I'm not good at Ruby and I wasn't able to test a patch for Yamazaki implementing comparison between torrents.
The lack of comparison was problematic, as Ruby was thinking equal Torrents (for us!) were different, making it think Yamazaki got new torrents
(and spamming the same torrents, again ;_;).

fix indentation

Add host OS recognition

Based Launchy. With this commit, Miyuki can recognize if she's running on mac, linux or whatever and give you the right notifier.

(probably) adapted to ruby guidelines, make Notifier methods static

Notifier#getNotifier and Notifier#OS are now static methods (and makes sense!)

Refactor notifications

Fix indentation of miyuki.rb

Fix indentation of miyuki.gemspec

Fix indentation of miyuki.gemspec

Fix indentation of miyuki.gemspec

Little changes before merging