WIP: Feature/fast scroll mute

[tobymitico]

I read contributing.md and I'm fully aware this may not be merging as is. I'm happy to make this PR a discussion and implement requested changes as we go. this PR helped me get slack-term a lot more usable on a slightly bigger workspace (aka long channel list and lots of notifications).

in a nutshell this PR adds:

• a fast scroll hotkey for faster scrolling through channels list
• proper muted channels handling and marking them somewhat similar to how the webUI does
• update slack-api to upstream 0.10 (and required patches that came with that)
• drop of vendor support

all of the above works but was just a quick and dirty way to get this going for me and read/learn the code base, but before I spend more time cleaning this up, I figured I start this discussion....

also what I'd still really like to find/fix is a way to limit the direct DM contacts in the channels list to those that are actually still open. it seems like none of the fields provided by the API identifies those?!?!. it seems any Contact every contacted is listed and that makes this list way longer than it needs to be.