Released Amethyst version 0.8 yesterday. It has some significant improvements to stability as well as adding a few new features. There's a new column layout that tiles windows into full height columns and the addition of floating windows. It can be downloaded here or installed via homebrew cask.
I had a request for floating windows and it's now in the app.
mod1 + t can be
used to toggle whether a window is tiled or floating. A floating window will not
be tiled, but will be part of the focus chain.
Additionally, you can supply a list of bundle identifiers for which windows will
be floating by default. They can be specified by defining an array of bundle
identifier strings under the
floating key in your
.amethyst file. Any
application matching a bundle identifier in the list will have its windows float
by default, though use of
mod1 + t will tile it if you want. I find this quite
useful for windows that Amethyst generally can't resize or position correctly