Fix README markdown

README.md

@@ -11,17 +11,20 @@ Thanks for using! :smile:
 
 [docker-hackmd](https://github.com/hackmdio/docker-hackmd)
 ---
+
 Before you go too far, here is the great docker repo for HackMD.
 With docker, you can deploy a server in minutes without any downtime.
 
 [migration-to-0.4.0](https://github.com/hackmdio/migration-to-0.4.0)
 ---
+
 We've dropped MongoDB after version 0.4.0.
 So here is the migration tool for you to transfer the old DB data to the new DB.
 This tool is also used for official service.
 
 Browsers Requirement
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+
 - Chrome >= 45, Chrome for Android >= 47
 - Safari >= 9, iOS Safari >= 8.4
 - Firefox >= 44
@@ -31,12 +34,14 @@ Browsers Requirement
 
 Prerequisite
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+
 - Node.js 4.x or up (test up to 6.2.2)
 - Database (PostgreSQL, MySQL, MariaDB, SQLite, MSSQL)
 - npm and bower
 
 Get started
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+
 1. Download a release and unzip or clone into a directory
 2. Enter the directory and type `npm install && bower install`, which will install all the dependencies
 3. Setup the configs, see more below
@@ -45,6 +50,7 @@ Get started
 
 Upgrade guide
 ---
+
 If you are upgrading HackMD from an older version, follow these steps:
 
 1. Fully stop your old server first (important)
@@ -57,7 +63,8 @@ If you are upgrading HackMD from an older version, follow these steps:
 
 Structure
 ---
-```
+
+```text
 hackmd/
 ├── tmp/            --- temporary files
 ├── docs/           --- document files
@@ -71,7 +78,9 @@ hackmd/
 
 Configuration files
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+
 There are some configs you need to change in the files below
+
 ```
 ./config.json			--- for server settings
 ./public/js/common.js	--- for client settings
@@ -79,6 +88,7 @@ There are some configs you need to change in the files below
 
 Client settings `common.js`
 ---
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 | variables | example values | description |
 | --------- | ------ | ----------- |
 | debug | `true` or `false` | set debug mode, show more logs |
@@ -87,6 +97,7 @@ Client settings `common.js`
 
 Environment variables (will overwrite other server configs)
 ---
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 | variables | example values | description |
 | --------- | ------ | ----------- |
 | NODE_ENV  | `production` or `development` | set current environment (will apply corresponding settings in the `config.json`) |
@@ -97,6 +108,7 @@ Environment variables (will overwrite other server configs)
 
 Server settings `config.json`
 ---
+
 | variables | example values | description |
 | --------- | ------ | ----------- |
 | debug | `true` or `false` | set debug mode, show more logs |
@@ -131,6 +143,7 @@ Server settings `config.json`
 
 Third-party integration api key settings
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 | service | file path | description |
 | ------- | --------- | ----------- |
 | facebook, twitter, github, gitlab, dropbox, google | `config.json` | for signin |
@@ -139,6 +152,7 @@ Third-party integration api key settings
 
 Third-party integration oauth callback urls
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+
 | service | callback url (after the server url) |
 | ------- | --------- |
 | facebook | `/auth/facebook/callback` |
@@ -150,9 +164,10 @@ Third-party integration oauth callback urls
 
 Operational Transformation
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+
 From 0.3.2, we started supporting operational transformation.
 It makes concurrent editing safe and will not break up other users' operations.
 Additionally, now can show other clients' selections.
-See more at http://operational-transformation.github.io/
+See more at [http://operational-transformation.github.io/](http://operational-transformation.github.io/)
 
 **License under MIT.**