Grammatical errors, spell corrections

[davesque]

What was wrong?

Noticed errant uses of "it's" as well as some other low-hanging fruit around those errors.

How was it fixed?

Fixed incorrect uses of "it's", made some spelling corrections, and made some minor style improvements for text that was close by.

Cute Animal Picture

[davesque]

I actually noticed a lot more spelling errors and typos. It would be good to go back over the docs with some kind of automatic tools for that at some point.

[davesque]

@carver @pipermerriam Any idea why this PR is failing on Travis? I can't gather much from the failure logs and I didn't make any changes to .py files outside of docstrings.

[pipermerriam]

Because populus is broken on master. Likely the new rlp 1.0 release.