Readme update

Versions marked all around

add webp write support

see libvips#65

I've updated the bundle and broken rspec, this needs fixing

we should probably have webp read as well I guess

Regenerate gemspec for version 0.3.9

Regenerate gemspec for version 0.3.8

Regenerate gemspec for version 0.3.7

Regenerate gemspec for version 0.3.6

Regenerate gemspec for version 0.3.5

Regenerate gemspec for version 0.3.4

Regenerate gemspec for version 0.3.3