2013 survey

[houhoulis]

• Calculate medians as well as average salaries.
• Decline to report results if there are 2 or fewer responses in any category, because e.g. reporting the average results of one respondent is not anonymized.
• Update specs to use expect syntax.
• More specs.
• Use a helper class instead of monkey-patching Array.

I have NOT included the actual anonymized survey data in this public repo. Will contact you privately.