Construct RECORD file using csv.writer

[frostming]

To correctly quote paths in the record entry.

Fix #117

[Hnasar]

The API isn't documented, but I'm not sure if it's used anywhere. I considered if this should instead issue a deprecation warning and keep the old function also, but it looks like this project doesn't mind slight breaking API changes (https://installer.readthedocs.io/en/latest/changelog/).

Edit: I see that these methods aren't listed in the public api in __all__, so it's fine.

So, this looks good to me! Thanks for investigating!

[frostming]

ping @pradyunsg , may I get a review for this PR? thanks.

[pradyunsg]

I'll cut a release with this over the weekend.