updated exam_processing, test_basic

test_basic is passing identify id, sng, grade under assumptions that id
is 8-digit value, grade is the column containing values belonging to
valid grade enumeration, and sng is clearly defined or is to the right
of grade
updated tests, exam_processing

fixed bugs in generate_csv, get_sng_by_id and get_grade_by_id. used
itertools for comparison in test_generate_csv
Merge branch 'master' of https://github.com/shopuz/exam_processing

Conflicts:
	exam_processing/exam_processing.py