Support for julia-0.7
Major changes:
- Dropped support for julia-0.6, moved on to julia-0.7
- Moved Plotting and BioBakery utilities out to separate packages to reduce dependencies
- These two new packages will be released shortly
- I'm keeping DataFrames dependency for now, though I'd like to move to IterableTables soonish (though constructors might be more sense in EcoBase)