Added fib solutions
Added query class solution
Fixed bug with limit
Changed filter to reflect change in problem example
Modified sort_by for q5 to take into account nil values
Added q2 as merge sort
Added q3 tree
Added csv
Added make change
Added alt solutions
Removed lecture code examples
Merge branch 'solutions' of github.com:Duke-PL-Course/Ruby

* 'solutions' of github.com:Duke-PL-Course/Ruby:
  Removed lecture code examples
  Added alt solutions
  Added make change
  Added csv
  Added q3 tree
  Added q2 as merge sort
  Modified sort_by for q5 to take into account nil values
  Changed filter to reflect change in problem example
  Fixed bug with limit
  Added query class solution
  Added fib solutions