Oreum-core

+ [x] made sample stepper explicit
+ [x] minor improvements to model plotting
+ [x] minor improvements to eda describe, display

No great changes from v0.4.0 just a general tidyup

+ New model reload capability
+ Improved file handling throughout
+ General consolidation throughout

+ [x] Minor updates to requirements
+ [x] improved `curate.SimpleStringIO`

+ [x] Overhauled `BasePYMC3Model` to save traces to `idata` only
+ [x] Overhauled `_create_idata` accordingly to allow creation from prior, trace or posterior idata with logical dependencies
+ [x] Overhauled `update_idata` accordingly to allow attaching an externally loaded idata object (model reinstantiation)
+ [x] Renamed all relevant functions to use `idata` rather than `azid`

+ dropped nltk and related text processing - will create a new package for that if needed
+ general tidy of unused imports
+ cleaned up inits