Cleanup back ticks and apostrophes

[elliotchance]

Backticks (`) and UTF-8 apostrophes should be replaced with regular apostrophes.

[mkim219]

Hi @elliotchance. Can I work on this issue?

[elliotchance]

@mkim219 yes - you don't need to ask permission, just put in a PR

[mkim219]

@elliotchance I have a question about this issue. If user inputs Backticks (`) and UTF-8 apostrophes, this should be converted into regular apostrophes?

[elliotchance]

Yes. So this really means backtick and variations of smart quotes - the 4 characters that make up the single and double for open an close. You might find this helpful: https://stackoverflow.com/questions/9401312/how-to-replace-curly-quotation-marks-in-a-string-using-javascript