Add more paragraph style attributes

[nuudles]

This commit adds several more attributes from the NSParagraphStyle properties, including the firstLineHeadIndent, headIndent, tailIndent, maximumLineHeight, minimumLineHeight, paragraphSpacing, and paragraphSpacingBefore properties. Unit tests have also been added to test these new properties.

[ZevEisenberg]

@nuudles ❤️ ❤️ ❤️ for the time you're putting into this! I'm going to be very busy until just after the new year, so I won't be able to give this a good look until then - sorry for the wait. Two things jump out after a quick peek, though:

1. It would be nice to differentiate between paragraphSpacingBefore and paragraphSpacingAfter. Apple's API isn't as clear as it could be, but we can use this opportunity to make it better.
2. BonMot's indentSpacer property uses headIndent internally to do its thing. Have you looked at cases where this might conflict with your headIndent property? Try it out in IndentationCell.m in the example project and see if you run into any interesting edge cases worth testing or throwing exceptions for.

[nuudles]

@ZevEisenberg Congrats dude! No worries on any delay, I know what it's like to plan one of those. I'll take a look at your initial feedback.

Cheers!

[ZevEisenberg]

@nuudles this all looks great, aside from my earlier comments.

[nuudles]

@ZevEisenberg Sorry for the delay in taking a look at this. Work got away from me. I've updated the name of paragraphSpacing to paragraphSpacingAfter. As far as the headIndent property, I spent some time with playing around with the indentSpacer property with headIndent and it seems that the indentSpacer always overwrites headIndent, which is probably as expected. Do you think we should add some documentation to that effect though so that the behavior is documented?

[ZevEisenberg]

@nuudles A little inline documentation would be appreciated. And if you've got the time, a unit test to make sure that behavior stays consistent. Thanks for getting back to this - always appreciated!

[ZevEisenberg]

Please rename the block typedef to match.

[nuudles]

@ZevEisenberg I've tried to add initial tests and documentation as requested regarding the headIndent and indentSpacer behavior. Unfortunately, I'll have limited time in the near future coming back to this if there are additional changes needed.

As a side note, going back to writing Obj C code after dealing with Swift for so long is harder than anticipated.

[ZevEisenberg]

@nuudles thanks. I'll take it from here if any additional changes need to be made. And I agree about writing Obj-C. I've only been doing Swift in a hobby project, but it's completely ruined me for remembering to put @ on NSString literals.

[ZevEisenberg]

@nuudles I made a couple of tweaks (1aa95e3...f1dfff2 - nothing major) and merged. Thanks for your contribution!

[nuudles]

@ZevEisenberg That's great! Thanks for implementing the tweaks for me!