Renamed FES date filtering function

`date_range` and `dateRange` functions renamed to `fes_date_filter`

Fixes #141
There is no ideal way of testing notebooks yet, like travis-ci is packages that contains a testing module.  However, we can make a habit of always sending a rendered nbviewer url when submitting PRs.  (That should be the very first thing a PR-reviewer should ask from the person submitting the PR.)

[This](https://addons.mozilla.org/en-US/firefox/addon/open-in-nbviewer/) firefox addon makes it easy to create nbviewer links. (Some of you probably already know and use it).  Once installed just go to the raw view of the `.ipynb` on github and click the addon icon to get the rendered url.  There is a Google Chorme version as [well](https://chrome.google.com/webstore/detail/open-in-nbviewer/ihlhlehlibooakiicbiakgojckpnlali).

PS: I will create a github emoji named :scowls_at_bad_practices: for situations like that :wink: