Implemented calendar search

-Calendar search is now available which will show minimum price for all
flights between a certain range of dates (calendar_query.html, new
solution_model classes, CalendarItaMatrixDriver)
-Refactor ItaMatrixDriver to use an AbstractItaMatrixDriver
-New query.html
-Rename flight_scraper/flight_scraper to flight_scraper/scraper
Merge pull request #2 from rockg/master

Implemented calendar search