This commit adds a dockerfile to install vmpooler without a local redis installation. Without this change the dockerfile provided assumes a local redis instance will be running. The dockerfile with redis is retained as 'Dockerfile-aio'. Additionally, the directory '/var/log/vmpooler' is no longer created since vmpooler uses '/var/log/vmpooler.log'.
Set to use a newer JRuby
Added an environment variable for the log file location
Changed entrypoint to cmd to add flexibility
Added missing trailing slash to copy command path
Built off the [jruby](https://hub.docker.com/_/jruby/) `Dockerfile`,
it installs gem requirements via `bundler`, installs and runs a
`redis-server`, imports the current working directory, starts
`vmpooler`, and tails the logfile.
Creating a `vmpooler.yaml` configuration file in the current working
directory and running the following provides a development environment:
```
docker build -t vmpooler . && docker run -p 80:4567 -it vmpooler
```
