Iteration 3 - When Searching w/ a Filter, UI should Indicate Hidden Results

[kienthuynh]

Summary

• When searching the teachers table with some status checkboxes unchecked, a notice now appears directly below the "Showing X to Y of Z entries" line indicating how many matching records are hidden by the current filter (e.g. 1 result(s) in Denied, 2 result(s) in Not Reviewed — hidden by current filter)
• 

Implementation Notes

• app/javascript/packs/datatables.js: Uses DataTables' public row().cache('search') API to count against pre-computed in-memory search data then injects notice text below the main results text
• features/step_definitions/table_steps.rb: Adds a new step definition that only populates the search for the teachers table, since the teachers index has both the teachers and admins tables

Testing

• Simple cucumber test included to make sure notice text appears with correct counts
• Deployed to Heroku: https://sp26-03-bjc-c7c152ebb984.herokuapp.com/teachers

@cycomachead @armandofox @mdawn65

[hagenhaeussler]

yep, looks all good