Clean up examples and README

[ajavadia]

This is a cleanup of some of the examples and the README given the recent issues (#344, #354, Slack messages).

• The hello_quantum example in the README is now more concise, and uses the QISKit interfaces better (instead of using QuantumProgram for everything).

• Increased timeout to 300 for the hello_quantum example.

• Removed the relative imports in all examples, and replaced with a note.

• General cleanup of README.

Description

Motivation and Context

How Has This Been Tested?

Screenshots (if appropriate):

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

Checklist:

• My code follows the code style of this project.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have read the CONTRIBUTING document.
• I have added tests to cover my changes.
• All new and existing tests passed.

[diego-plan9]

Thanks @ajavadia - removing the sys.path mangling and also taking the chance to start the moving away from QuantumProgram is awesome! 👍