Update README.md to convey latest project status

[daviwil]

Also introducing the new Development Roadmap wiki page. @rkeithhill, would appreciate your feedback on what I've laid out there so far. Feel free to add new items that you're interested in working on.

[rkeithhill]

Looks good. I was going to mention attaching the debugger to a runspace (both local and remote) but I see you have that in 0.7.0. Do you think conditional breakpoint support is something easy enough for me to do in 0.4.2 or should that wait until 0.5.0? As for doc strategy, what do you think about using DocFX?

[daviwil]

Since conditional breakpoint would be a new feature, I'd say lets leave it for 0.5. If you're interested in working on remote session debugging sooner than 0.7, I'm fine with that! I had originally put it in 0.6 but wasn't sure if it was too early. Totally up to you. PoshTools' codebase has a pretty good example of how to accomplish this.

DocFX looks sweet, I've looked at in the past and liked what I saw. I'll need to talk to Joey to see if we need to use do something that fits in with the new PowerShell documentation strategy. We'll have to play around with some options in the next couple months.