Rename Sections 2 and 3 in README

[dvenprasad]

Please provide some background on the proposed additions or changes.

The titles of each of section is a step to take to run the workflow. Sections 2. Input Data Format and 3.Metadata File Format does not indicate what action is expected of users

Please describe the proposed solution. Rename the sections to be action oriented than subject oriented.

For example, we can rename the sections to:

2. Verify Input Data Format
3. Create Metadata File

[cbethell]

Addressed by #328