Clean control chars from issue body field

[laurentS]

Fixes #44

I've run the stream on just over 200k issues to test and have not seen any problems so far (including the one that was causing the problem in the first place).
The check for an empty body puzzles me a bit, but the tap failed almost immediately without it.

[aaronsteers]

@laurentS - Approved - thanks for the detail around tests run. Are you able to merge once action items and approvals are in? If not, just lmk when this is ready to go and I'll merge with your blessing. Thanks!

[laurentS]

Nope, I'm not allowed to merge, but happy for you to do it :)

[aaronsteers]

Done! Just as an FYI, in general, our Meltano PR etiquette is to wait for an explicit invitation to merge from the author. Unless there's a reason to move forward with haste, we wait for the invitation to avoid accidentally merging something where the author intended another small tweak before merging.

fyi - @pnadolny13 and @tayloramurphy - We may eventually want to create an adapted version of PR / Github etiquette for MeltanoLabs, just a thought. Could borrow from here but may have some differences: https://handbook.meltano.com/engineering/#responsibility-to-merge