Remove ebuilds for old versions.

We should not use these versions now.

Memorials: Rust 0.8 was released on Sep 27, 2013. Rust 0.9 was done on
Jan 10, 2014.

Signed-off-by: OGINO Masanori <masanori.ogino@gmail.com>
Add .travis.yml to check ebuilds using repoman.

Based on the .travis.yml in @mrueg's overlay. Thank you!

Signed-off-by: OGINO Masanori <masanori.ogino@gmail.com>