Update README.md

Combined Ubuntu and Debian installation method as it is basically the same.

Other changes:
* Replaced "Bittorrent" with "BitTorrent";
* Replaced "btsync" with "BitTorrent Sync";
* Some minor changes.
Update README.md
Update README.md

Fixed an error
Update README.md

Separated Ubuntu and Debian back, as suggested by @tuxpoldo.
Update README.md

Debian: Added "powerpc" in the list of supported platforms (not present in the current readme).
Merge pull request #27 from leoetlino/patch-2

[Minor changes] Update README.md