memoize get_holiday method
rename max to to may_days
update check_leave_bal script
change find_end_date script to use POSt
update var names in leave_request script
check leave days
helper methods for listing subordinates and leave types
add leave_type assoc. to LeaveRecord
move js to close of body tag
change leave_requests collection routes to POST
script to enable/disable btns based on leave bal
update leave_request form to include helper methods
updates to LeaveRequests controller

- User can save book leave
- Check leave days available and display appropriate messages
- Check maximum days a user can book leave for
- Display readonly/disabled inputs and pre-fill text inputs based on number of leave days left