Added a simple docker run example doc

docs/docker-run.md

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+# Docker images
+Docker images are available on Docker Hub at [electriccoinco/lightwalletd](https://hub.docker.com/repository/docker/electriccoinco/lightwalletd).
+
+## Using command line options
+
+Already have a zcash node running with an exposed RPC endpoint?
+
+Try the docker container with command lines flags like:
+```
+docker run --rm -p 9067:9067 \
+  electriccoinco/lightwalletd:v0.4.2 \
+  --grpc-bind-addr 0.0.0.0:9067 \
+  --no-tls-very-insecure \
+  --rpchost 192.168.86.46 \
+  --rpcport 38237 \
+  --rpcuser zcashrpc \
+  --rpcpassword notsecure \
+  --log-file /dev/stdout
+```
+
+## Preserve the compactblocks database between runs
+
+Like the first example, but this will preserve the lightwalletd compactblocks database for use between runs.
+
+
+Create a directory somewhere and change the `uid` to `2002`.  
+The is the id of the restricted lightwalletd user inside of the container.  
+
+```
+mkdir ./lightwalletd_db_volume
+sudo chown 2002 ./lightwalletd_db_volume
+```
+
+Now add a `--volume` mapping from the local file path to where we want it to show up inside the container.
+
+Then, add the `--data-dir` to the lightwalletd command with the value of path mapping as viewed from inside the container.
+
+```
+docker run --rm -p 9067:9067 \
+  --volume $(pwd)/lightwalletd_db_volume:/srv/lightwalletd/db_volume \
+  electriccoinco/lightwalletd:v0.4.2 \
+  --grpc-bind-addr 0.0.0.0:9067 \
+  --no-tls-very-insecure \
+  --rpchost 192.168.86.46 \
+  --rpcport 38237 \
+  --rpcuser zcashrpc \
+  --rpcpassword notsecure \
+  --data-dir /srv/lightwalletd/db_volume \
+  --log-file /dev/stdout
+```
+
+
+## Using a YAML config file
+
+When using a configuration file with the docker image, you must create the configuration file and then map it into the container. Finally, provide a command line option referencing the mapped file location.
+
+Create a configuration file:
+```
+cat <<EOF >lightwalletd.yml
+no-tls-very-insecure: true
+log-file: /dev/stdout
+rpcuser: zcashrpc
+rpcpassword: notsecure
+rpchost: 192.168.86.46
+rpcport: 38237
+grpc-bind-addr: 0.0.0.0:9067
+EOF
+```
+
+Use it with the docker container
+```
+docker run  --rm \
+    -p 9067:9067 \
+    -v $(pwd)/lightwalletd.yml:/tmp/lightwalletd.yml \
+    electriccoinco/lightwalletd:v0.4.2 \
+    --config /tmp/lightwalletd.yml
+```
+
+## Using docker-compose for a full stack
+
+Don't have an existing zcash node? Check out the [docker-compose](./docker-compose-setup.md) for examples of multi cantainer usage.