Remove trailing whitespace
Update headers

* Make the headers (mostly) hierarchical.
* Replace horizontal lines with headers in the Niceties section.
Remove reference to BIG_FREE_READER shutdown

It's been down for quite some time now.
Adjust whitespace, add punctuation
Update paragraph about API key
Merge pull request #300 from Koronen/update-readme

Update README
Manually fix merge of Readme.md