spikeforest2 ironclust update procedure

[Compile ironclust2]
1. Run `irc_mcc` in `ironclust/matlab`
2. Run `copyfile run_irc ~/src/spikeforest2/spikeforest2/sorters/ironclust/container`

[Build the docker in spikeforest2]
3. Run `cd-spikeforest2`
4. Run `cd spikeforest2/sorters/ironclust`
5. Edit ironclust version numbers in `_ironclust.py`
6. Run `cd container`
5. Edit ironclust version numbers in `build_docker.sh` and `push_docker.sh`
5. Run `./build_docker.sh && ./push_docker.sh`

[Test and push to git]
6. Run `cd ~/src/spikeforest2/examples` 
7. Run `python example_ironclust.py` (set `HITHER_USE_SINGULARITY=TRUE` in .bashrc)
8. Run `git add -u. && git commit -m "ironclust updated" && git push`