wrote a readme

README.md

@@ -8,3 +8,54 @@ issues](https://img.shields.io/github/issues/docwhat/docker-gc.svg)](https://git
 # Docker GC
 
 > The missing garbage collector for docker
+
+## Installation
+
+### Binaries
+
+I have pre-built binaries for several platform already.  They are available on
+the [releases page](https://github.com/docwhat/docker-gc/releases).
+
+### Source
+
+If you have go installed, then you can get the binary `docker-gc`
+with the following command:
+
+``` .sh
+$ go get -u docwhat.org/docker-gc/bin/docker-gc
+```
+
+Usage
+-----
+
+~~~
+usage: docker-gc [<flags>]
+
+The missing docker garbage collector.
+
+Flags:
+  -h, --help                Show context-sensitive help (also try --help-long
+                            and --help-man).
+      --version             Show application version.
+  -m, --max-image-age=168h  How old to allow images to be before deletion. (Env:
+                            DOCKER_GC_MAX_IMAGE_AGE)
+  -s, --sweeper-time=15m    How much time between running checks to delete
+                            images. (Env: DOCKER_GC_SWEEPER_TIME)
+  -v, --verbosity=1         How much logging to stderr. 0 = none. 9 = maximal
+                            (Env: DOCKER_GC_VERBOSITY)
+~~~
+
+It uses the normal Docker environment variables, so if `docker info` works,
+then `docker-gc` should work.
+
+Developers
+----------
+
+I use a `Rakefile` to build and test.
+
+Install [Ruby](https://www.ruby-lang.org/) and you can setup, test and lint the
+code.
+
+~~~
+$ rake setup test lint
+~~~