Reduce size of examples/simplify naming

[samzipper]

Suggest trimming the example down to a smaller file covering a shorter time duration, but should still include both wet and dry periods.

Also, perhaps change test data file names to be shorter and more descriptive of content. Maybe something like:

• raw_hobo_data
• tidy_stic_data
• calibrated_stic_data
• calibration_standard_data Something like that?

[christopherwheeler]

Shortened and changed example df names to those you suggested!