Add tests to test function to structure PSI data extracted from an HTML table

Disable get_psi_page() test.

References #5
Fix incorrectly named variable for PSI 24 hour collection.

References #5
Add simple case for structure_table(). Fill in test for structure_table() for 24 hour PSI data.

References #5
Complete structure_table() so it passes the test.

References #5
Refactor. Pull out duplicate code in preparing the output dictionary structure.

Use a helper function to populate data from the separate halves into the output dictionary.

References #5.