Spreadsheet download doesn't contain headers or all rows

[jonespm]

In testing, we noticed that when downloading a spreadsheet for a cohort it doesn't include and headers and only includes two rows. It should probably have both of these features in the spreadsheet.

To reproduce:

• As admin, go to manage and select a cohort
• Click the button on the top to download the cohort xls

The file downloaded should more closely match what's on the page