Standardizing capitalization
Standardizing capitalization

* All mentions of `python` (lowercase) as `Python` (titlecase) in accordance with [their own style](https://www.python.org/).
* Standardized the `/r/` to `r/` prefix as the latter is the standard usage now according to Reddit.
* Capitalize `Gitter` in accordance with [their own style](https://gitter.im).
praw-dev/praw,gschizas/praw,praw-dev/praw,gschizas/praw