Jimmy/jimmy rustdoc to alpha.8

[JoshOrndorff]

Thanks for looking at this Jimmy. I'm torn about whether to merge this as it is because it refactors code on master. Since adopting gitflow (general explanation, recipes contributing guide), I've been trying to keep refactors to the develop branch. That being said I do want to get the links fixed to unblock @danforbes in removing substrate.dev/rustdocs/master So I guess there are a few ways to proceed.

1. Just merge this even though it isn't strictly gitflow. But it leaves the problem that the changes are not on develop.
2. Copy these changes to develop instead (I would do that work). And separately fix the links on master (would need your help there).
3. Copy these changes to develop (I would do that work). And leave these two links broken on master

I guess maybe I've already done something wrong because I wasn't able to just rebase this on top of develop without a billion merge conflicts.

[JoshOrndorff]

Okay, I've decided to go with either 2 or 3. I've copied (technically git cherry-picked) the changes into #260 and merged it into develop. So, @jimmychu0807 your changes are safely committed and merged there. Thank you for making them.

I'm going to close this PR because I don't want to merge code refactorings to master without going through develop first. Actually, it's less about blindly sticking to a process and more about there isn't a good way to get those changes back into develop if they're merged here.

I discussed this with @danforbes and want to document a few points we hit on here:

• This situation could potentially be avoided if master branch took its dependencies from github rather than crates.io.
• If master takes its dependencies from github, then I don't see any reason to have the overhead of gitflow. We could just fall back to a simple merge-prs-into-master workflow. The reason I was moved to use gitflow in the first place was to simultaneously be proactive (rather than reactive) about keeping up with Substrate's changes, and take dependencies from crates.io
• I feel like the gitflow experiment is just beginning, so I don't want to bail on it yet. This experience is one strike against it, but I want to keep trying at least for now.

[jimmychu0807]

Cool. Thanks for picking back my changes. From now on, I will work off from develop branch. gitflow looks complicated and a lot of branches management. But as you said, let's try it out and see if we can benefit from it.