Bump the major version because:

- Ryu fully support OpenFlow 1.0, Nicira Extensions, and OpenFlow 1.2.
- Ryu was tested with various OpenFlow Hardware switches.
- There is lots of improvement since the last release.

Ryu is usable now so let's use the major version that implies so.

Signed-off-by: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>