Infrastructure: Only package algosdk in setup.py

[algochoi]

This PR fixes setup.py so only algosdk and its subdirectories are installed.

Locally tested:

• Delete *.egg-info and build directories
• Run pip install .
• Check that only algosdk is included in the install in site-packages. tests and examples are no longer shipped with the installation, which may address Move/rename "tests" module #374 as well.

Closes #408

[tzaffi]

I tested py preparing requirements.txt files pointing to the following alternatives:

• py-algorand-sdk@git+https://github.com/algorand/py-algorand-sdk@develop
• py-algorand-sdk@git+https://github.com/algorand/py-algorand-sdk@package-algosdk

I confirmed that pip install -r on the second did not include tests under site-packages but the first DID.

BTW, neither includes the examples directory.