Gneiss

* Added `balance_boxplot` and `balance_barplot` to make interpretation balance partitions easier.
* Added `balance_summary` to summarize a given balance using the q2 cli.
* Added `assign_ids` command to allow for ids to be added manually.

* Added q2 support for linear regression and linear mixed effects models [98](https://github.com/biocore/gneiss/pull/98)
* Added q2 support hierarchical clustering [116](https://github.com/biocore/gneiss/pull/116)
* Added interactive heatmaps with highlights with matplotlib [114](https://github.com/biocore/gneiss/pull/114)
* Added tree visualizations for unrooted trees with bokeh [112](https://github.com/biocore/gneiss/pull/112)
* Added support of cross validation for ordinary least squares [101](https://github.com/biocore/gneiss/pull/101)

* Added heatmap dendrogram plotting functionality [87](https://github.com/biocore/gneiss/issues/87)
* Added principal balance analysis heuristic using proportionality and wards clustering algorithm [83](https://github.com/biocore/gneiss/issues/83)

Features
* Added filehandle support for write and read io in RegressionResults object [77](https://github.com/biocore/gneiss/issues/77)

Features
* Added write and read io for RegressionResults object [72](https://github.com/biocore/gneiss/issues/72)

Features
* Added `ladderize` and `gradient_sort` [29](https://github.com/biocore/gneiss/issues/29)

Bug fixes