Demo for nbgrader convert dataset to notebooks

[rameshjes]

• Creating the separate notebook for each student with question and answers(in raw folder there is answer and question file) (either automate it using nbformat or manually)
• Adding the create assignment cell toolbar in all and marking it as Manually graded.
• Release the assignment.

[rameshjes]

Issue resolved

Instructor versions: https://github.com/rameshjesswani/Semantic-Textual-Similarity/tree/master/source/assignment01

Student versions: https://github.com/rameshjesswani/Semantic-Textual-Similarity/tree/master/release/assignment01