Inconsistent output when measuring diversity

[richardreeve]

Measuring a single diversity of a supercommunity generates a number, vector or matrix, depending on what is being measured. Furthermore, measuring several diversities simultaneously generates a vector of these. We need a common output format for all diversity measurements, and the most sensible is a DataFrame for now.

• Decide on a standard output for diversity calculations
• Implement for individual inddiv() calculations along with tests
• Implement for individual subdiv() calculations along with tests
• Implement for individual metadiv() calculations along with tests
• Implement for diversity()
• Ecology.jl
• Jost.jl
• Hill.jl

[richardreeve]

#13 Separation PR now fixes all of these issues.