Installing from Git shows no kernels except python3

I'm trying to build BeakerX from source, hopefully to get autocomplete for Scala. The last release from Conda has no auto-complete unfortunately.

Following these instructions after I cloned the repo.

**Build and Install (linux and mac)**
```
conda env create -n beakerx -f configuration.yml
conda activate beakerx # For conda versions prior to 4.6, run: source activate beakerx
(cd beakerx; pip install -r requirements.txt --verbose)
beakerx install
beakerx_databrowser install
```

I end up with a beakerx only with the Python3 kernel. So I went into `beakerx/kernel` and did `cd kernel; ./gradlew build` to build the JVM based kernels (hopefully scala, groovy, clojure, java). That didn't do it. So I looked at issues and found that I can run this
```
jupyter kernelspec install --sys-prefix --replace --name scala /Users/lef/git/beakerx/kernel/scala
```
Which contains the kernel.json file and I have already generated JARs with gradle. But nothing. Whenever I try to open a Scala notebook, it says "scala kernel not found" and shows me Python3.

I am on a MacOSX, any help to get scala installed with autocomplete would be great. I would also like to be able to `sbt install` for that scala, but maybe that's a long shot.