Implement private method _switch(lever) skeleton
* change data structure to array of -1 and 1
* makes it easier to switch signs later
Fix display to match new -1/1 format for gates
Simple implementation of opening/closing doors
* simple error handling if number entered is not in range
Complete first implementation of level
Rename gates to positions
* add incrementing moves variable to keep track of score
Number of moves made listed below gate graphic
Change game rules slightly
* don't punish player for entering a number out of range
Add custom messages depending on moves taken
* only pass in needed attributes to display
Extract print_moves into new method
* fix small argument error in print_gates