Update README.md

Updated formatting instructions (with thanks to Norman Dunbar).
Update README.md

Added screenshot to README
Merge branch 'dev' of https://github.com/raspberrypi/recovery - fixes #3
Completing portuguese translation
Merge pull request #12 from lucastsa/master

Fix up Portuguese translation thanks to @lucastsa
Merge branch 'dev' - fixes issues #7 and #11