add the notice of checkstyle (#2983)

* add the notice of code style

* modify the pic

* del teh faq.md, move to dubbo-website

CONTRIBUTING.md

@@ -63,4 +63,14 @@ Thanks for contributing!
 ### Code style
 
 We provide a template file [dubbo_codestyle_for_idea.xml](https://github.com/apache/incubator-dubbo/tree/master/codestyle/dubbo_codestyle_for_idea.xml) for IntelliJ idea, you can import it to you IDE. 
-If you use Eclipse you can config manually by referencing the same file.
+If you use Eclipse you can config manually by referencing the same file.
+
+**NOTICE**
+
+It is very important to set the dubbo_codestyle_for_idea.xml, otherwise you will fail to pass the Travis CI. Steps to set the code style are as below:
+
+1. Enter `Editor > Code Style`
+2. To manage a code style scheme, in the Code Style page, select the desired scheme from the drop-down list, and click ![manage profiles](codestyle/manage_profiles.png).
+From the drop-down list, select `Import Scheme`, then select this option `IntelliJ IDEA code style XML` to import scheme
+3. In the Scheme field, type the name of the new scheme and press ⏎ to save the changes.
+

FAQ.md

@@ -1,25 +0,0 @@
-### Where is dubbo-admin?
-
-dubbo-admin has been moved from core repository to https://github.com/apache/incubator-dubbo-ops since 2.6.1
-
-### Which version should I choose?
-
-Currently, dubbo keeps 3 versions evolve in parallel:
-
-* 2.7.x (master): requires Java 1.8, major feature branch.
-
-* 2.6.x: requires Java 1.6, minor feature & bugfix branch, GA, production ready.
-
-* 2.5.x: requires Java 1.6, maintenance branch, only accept security vulnerability and critical bugfix, expected to be EOL soon.
-
-check [this](https://github.com/apache/incubator-dubbo/issues/1208) for detailed version management plan.
-
-For contributors, please make sure all changes on the right branch, that is, most of the pull request should go to 2.7.x, and be backported to 2.6.x and 2.5.x if necessary. If the fix is specific to a branch, please make sure your pull request goes to the right branch.
-
-For committers, make sure select the right label and target branch for every PR, and don't forget to back port the fix to lower version is necessary.
-
-####  How to register ip correctly in docker?  
-
-[Example question](https://github.com/alibaba/dubbo/issues/742)  
-
-Dubbo supports specifying ip/port via system environment variables, examples can be found [here](https://github.com/dubbo/dubbo-samples/tree/master/dubbo-samples-docker).