README: Tweak bookmarklets

README: Clarify that the `INSERT` statement is there for a reason

Add nginx.conf

Update placeholder values to encourage HTTPS usage

Use HTTPS Twitter URLs by default

Prevent XSS attacks introduced by 213a24a1

Remove GPL license

Avoid re-shortening URLs

Use MySQL’s `utf8mb4` instead of `utf8`

Dual license this code under the MIT and GPL licenses

README: Add Tomislav Biscan as a contributor

Order by date and by slug, to handle the edge case where the last two entries have the same date

Update example `GOOGLE_PLUS_ID` to match my new G+ account.

Typo in README: `@` and `+` are still ignored in slugs that contain other characters.

Redirect http://example.org/@ to a specified Twitter profile.