Remove duplicate rule descriptions

[nzakas]

For the rule documentation page, there are currently two descriptions being shown: one right under the page title and one under the table of contents. Two tasks for each rule:

1. The one under the table of contents is hardcoded into the markdown files and should be removed. These files are all in docs/src/rules.
2. The one under the title is pulled from the rule's meta information, so we need to go through and capitalize those descriptions. These files are all in lib/rules.

[amareshsm]

I would like to work on this. I will send a PR.

[nzakas]

Thanks!