Further 0.7 updates, fix PackageEvaluator.jl

• Fix iterator issues with Julia 0.7
• PackageEvaluator should no longer reject package tests

Updates to prepare for 0.7

• Remove Nullable and replace with Union{T, Missing} for 0.7
• Base.Test -> Compat.Test
• Fix R igraph test errors for 0.6
• Update RCall to 0.10.0 with Missing

Add in Phylogenetic diversity and move to Julia v0.6

A major update to the codebase:

• Add general API for adding in new types of diversity, and interface for users to access it
  • Provides phylogenetic diversity measures through Diversity.Phylogenetics submodule
• Now Julia v0.6 (and mostly nightly) compliant, drop support for Julia v0.5
• Provides iterators for species and subcommunities
• Removes deprecated syntax from Diversity v0.2.x

Release v0.3.1 - validate against R boydorr/rdiversity package

This package is now in beta - it successfully validates against the R package boydorr/rdiversity.

Update input and output formats and add 0.6 compatibility

• Update input format and deprecate old format
• Update output format to use DataFrames
• Remove deprecations for Julia v0.6 and drop v0.4