[cli] refactor the LambdaPackage to use setuptools for function management

[ryandeivert]

related to: #1153

Background

The current LambdaPackage class has a fairly janky method of managing dependencies and creating deployment packages.

Proposal

• Add a setuptools setup.pyto each streamalert/<function>/ directory (where <function> is a directory for any lambda function code)
  • Note: this might require a change to the folder structure. Alternatively, we could create a lambdas directory or something similar that just implements the handlers and imports code from other packages (?)
• Have the setup.py for each lambda function define the required libraries needed. We would also specify data_files for setuptools to include config/etc. This all is currently done in a jank way here:

  streamalert/streamalert_cli/manage_lambda/package.py

  Lines 191 to 198 in 9718c28

  	package_files = {
  	'conf',
  	'streamalert/__init__.py',
  	'streamalert/classifier',
  	'streamalert/shared',
  	}
  	package_name = 'classifier'
  	package_libs = {'jmespath', 'jsonlines'}

• Use pip to install from each function's setup.py to target install to a directory.
• Remove the "zipping" logic we currently have for creating the archive in favor of using the archive_file feature in Terraform.

Note

This would require(?) the use of vagrant for installing via pip. See #1153