Improve overall CHANGELOG formatting and consistency for 3.0

[nicoddemus]

Tried to improve overall consistency and formatting of the CHANGELOG for 3.0. Suggestions are welcome!

Rules I tried to follow:

• Use past or imperative tense ("removed", "add");
• Reference issue ids at the end of the item;
• Finish all items with .;

[The-Compiler]

I think it should explicitly say "Python 3 versions < 3.3" (or just "Python 3.0 - 3.2" or so?), otherwise this might imply we dropped 2.7 😉

[The-Compiler]

Also the parens in "addressing (#1234)" don't make any sense. I'm really not sure where this came from - maybe because older changelog entries said "[Added a] fix (...) for some issue" and then it got cargo-culted and also used like "Fixes (...)" and "addressing (...)". Anyways, we should get rid of it IMHO.

[The-Compiler]

Seems like there are various places saying "for PR" and "for bug report", I didn't comment on all of them - maybe just add a "the" everywhere 😉

[nicoddemus]

Seems like there are various places saying "for PR" and "for bug report", I didn't comment on all of them - maybe just add a "the" everywhere 😉

Done!

We're probably getting into bikeshedding here

Not at all, I appreciate the review. 😁

[coveralls]

Coverage remained the same at 92.225% when pulling 4a763ac on nicoddemus:changelog-formatting into 54ea27c on pytest-dev:features.

[nicoddemus]

@The-Compiler could you merge if you don't have any other comments? I would like to get this in ASAP otherwise chances for conflicts with other PRs increases as time passes. 😁

[The-Compiler]

And in it is! Thanks!

[nicoddemus]

😄 👍