Documentation: Write Parley Motivation/Introduction Section

[DiogenesAnalytics]

Problem

While the current README.md documents usage and development, it is lacking the "motivation" behind the project: what problem does this software aim to solve?

Solution

Need to add an introduction section where this is discussed.

[DiogenesAnalytics]

Implemented with: 14c74fa0638738a0f27e57a722249fbfd67bc776