Docker関連の修正 (#2997)

* Modify Dockerfile and docker-compose.yml

* Fix MongoDB connection error
* Use alpine-3.8 instead of alpine-edge as base image
* Modify install packages
* Modify Mongodb image tag name

* Update Docker documents

* Add 'Download misskey' paragraph

* Make redis optional for Docker

docs/docker.en.md

@@ -7,23 +7,29 @@ This guide describes how to install and setup Misskey with Docker.
 
 ----------------------------------------------------------------
 
-*1.* Make configuration files
+*1.* Download Misskey
+----------------------------------------------------------------
+1. `git clone -b master git://github.com/syuilo/misskey.git` Clone Misskey repository's master branch.
+2. `cd misskey` Move to misskey directory.
+3. `git checkout $(git tag -l | grep -v 'rc[0-9]*$' | sort -V | tail -n 1)` Checkout to the [latest release](https://github.com/syuilo/misskey/releases/latest) tag.
+
+*2.* Make configuration files
 ----------------------------------------------------------------
 1. `cp .config/example.yml .config/default.yml` Copy the `.config/example.yml` and rename it to `default.yml`.
 2. `cp .config/mongo_initdb_example.js .config/mongo_initdb.js` Copy the `.config/mongo_initdb_example.js` and rename it to `mongo_initdb.js`.
 2. Edit `default.yml` and `mongo_initdb.js`.
 
-*2.* Configure Docker
+*3.* Configure Docker
 ----------------------------------------------------------------
 Edit `docker-compose.yml`.
 
-*3.* Build Misskey
+*4.* Build Misskey
 ----------------------------------------------------------------
 Build misskey with the following:
 
 `docker-compose build`
 
-*4.* That is it.
+*5.* That is it.
 ----------------------------------------------------------------
 Well done! Now, you have an environment that run to Misskey.