Merge code style and best practices

[ZevEisenberg]

We used to have separate code style and best practices documents for the Objective-C style guide, and they quickly got messy because there was no clear guideline for which document a new rule should go in. We ended up merging them into one document.

[agrosner]

#2

[ZevEisenberg]

@agrosner #2 does not appear to address this.

[agrosner]

ah mybad I misread the title.