implement add_new

[AdamGold]

if add_new=True, a generator will be made of all top tree dependencies - filtered by only non existing packages in setup.py. Then, add them (by regex, maybe AST in the future) to install_requires by the following logic:

1. search for install_requires=
2. search for the next comma that isn't followed by quotes (for example:
   install_requires=['test', 'test2'], # THIS COMMA test_requires)
3. ask the user if he/she wants to add all non existing packages or loop through.
   if all - just make a list from the generator and add before that comma. If it's a loop, loop through the generator, asking the user whether to add a specific package each time - make a list and add before that comma.
4. write to setup.py