Merge pull request #22 from nickdotreid/assignments

Fixed bug in Ajax.py
fixed content errors to resolve issues/17 and to get rid of while loops in files chapter and get rid of glossary entry for call graph which comes before functions have been introduced
add first review problems
Merge pull request #23 from aerenchyma/add_review_prblms1

Add first review problems
small changes to Review exercises
PS4 draft added to assignments
revised Functions chapter, part I
made language for test_questionfunctions_2a and 2b more clear
got rid of str+int issue in ch04_square
removed exercise header (because there are no exercises)
made last two questions func-12 and 14 get compiled
fixed test_functions_2_4
removed test_questionfunctions_2_1 because it was not covered in the chapter
added assignment/student page which will house grades for all assignments
added grade link to index
added grade controller
added grade query to assignment page
moved student view to index and index to admin
added list of students to admin page
added view for index.html