Dataset variable names different than the rest of the workshop

[brownsarahm]

The syntax of the variable names is different in this lesson than openrefine and what is listed on the data reference page. Some copies of it have alphanumeric prefixes on the meaningful names (in the python lesson, especially). It would help create more continuity for learners to use the same column names across (since it's the same dataset) the lessons. Also the alphanumeric prefixes in this lesson don't add useful information and do add more space for typos.