Ep2: Updating + adding links (and a citation) in "Our Data" section

[kthrog]

This issue is tied to Episode 2, Starting with Data, specifically the section "Our Data."

I'm proposing several updates and additions to clean up the links in this section as well as to add a full academic citation for the cited work. This includes:

1. Update the first link -- which is currently set to go to http://www.esapubs.org/archive/ecol/E090/118/default.htm but is actually re-directing users to https://esapubs.org/archive/ -- to the DOI for the paper in the link text, which is https://doi.org/10.1890/08-1222.1.
2. Edit the first sentence to add a full citation. For example (to note: the reference could be added at the end of the episode, and any citation style could be used; below is in APA):

For this lesson, we will be using Portal Teaching data, a subset of the data from the study, "Long-term monitoring and experimental manipulation of a Chihuahuan Desert ecosystem near Portal, Arizona, USA" (Ernst et al., 2009).

Reference: Ernest, S. M., Valone, T. J., & Brown, J. H. (2009). Long‐term monitoring and experimental manipulation of a Chihuahuan Desert ecosystem near Portal, Arizona, USA: Ecological Archives E090‐118. Ecology, 90(6), 1708-1708. https://doi.org/10.1890/08-1222.1

3. Instead of linking users right out to the download link (which always makes me nervous in the event of accidentally downloading something I shouldn't), link them to the [file's info page](https://figshare.com/articles/dataset/Portal_Project_Teaching_Database/1314459?file=10717177) and instruct people to download the surveys.csv file from the info page.

Full example of all proposed edits to text:

For this lesson, we will be using Portal Teaching data, a subset of the data from the study, "Long-term monitoring and experimental manipulation of a Chihuahuan Desert ecosystem near Portal, Arizona, USA" (Ernst et al., 2009).

We will be using files from the Portal Project Teaching Database. This section will use the surveys.csv file, which can be accessed, viewed and downloaded from here: https://figshare.com/articles/dataset/Portal_Project_Teaching_Database/1314459?file=10717177. If you prefer to download the file directly, you can do that using this link (note that a dialog box prompting you to download a CSV file may pop up on your device): https://ndownloader.figshare.com/files/2292172

Reference:

Ernest, S. M., Valone, T. J., & Brown, J. H. (2009). Long‐term monitoring and experimental manipulation of a Chihuahuan Desert ecosystem near Portal, Arizona, USA: Ecological Archives E090‐118. Ecology, 90(6), 1708-1708. https://doi.org/10.1890/08-1222.1