Bugfixes and other improvements

Major changes:

• fix bug when multiple SDP ctrs are used
• add explicit requirements.txt
• change the errors thrown for easier catching by the user

Minor changes

• refactoring and printing touch ups, license statements, adding long description for PyPI, adding PyPI badge to readme

v0.9.1

Adds some functionality for returning the NEOS job ID and password, which can be useful for debugging purposes. See the solve_neos module, function handle_submission (to just return ID and password after submitting) and new argument return_jobid_pwd for neos_solve (to track the solve until it finishes and return the message along with the ID and password. Backwards compatible with code written for previous versions.

Also includes some touch ups to documentation, printing, and package info.