bemenu: add options to specify more colors

[t-8ch]

Thanks @sinanmohd .

I think this also needs a bump to the required version of the bemenu dependency.

At least to 0.6.8, but I only checked cursory on my phone. If you could doublecheck this and update the PR that would be great.

[sinanmohd]

--cb and --cf was added on 6.10

https://github.com/Cloudef/bemenu/compare/0.6.9...0.6.10

[t-8ch]

Thanks! I'll cut a release later today.