Update README with 3.4.x (OpenAPITools#1162)

* update README with 3.4.x

* fix div

.github/PULL_REQUEST_TEMPLATE.md

@@ -2,7 +2,7 @@
 
 - [ ] Read the [contribution guidelines](https://github.com/openapitools/openapi-generator/blob/master/CONTRIBUTING.md).
 - [ ] Ran the shell script under `./bin/` to update Petstore sample so that CIs can verify the change. (For instance, only need to run `./bin/{LANG}-petstore.sh` and `./bin/security/{LANG}-petstore.sh` if updating the {LANG} (e.g. php, ruby, python, etc) code generator or {LANG} client's mustache templates). Windows batch files can be found in `.\bin\windows\`.
-- [ ] Filed the PR against the [correct branch](https://github.com/OpenAPITools/openapi-generator/wiki/Git-Branches): `master` (3.3.x), `4.0.x`. Default: `master`.
+- [ ] Filed the PR against the [correct branch](https://github.com/OpenAPITools/openapi-generator/wiki/Git-Branches): `master`, `3.4.x`, `4.0.x`. Default: `master`.
 - [ ] Copied the [technical committee](https://github.com/openapitools/openapi-generator/#62---openapi-generator-technical-committee) to review the pull request if your PR is targeting a particular programming language.
 
 ### Description of the PR

README.md

@@ -7,6 +7,11 @@
 [![Run Status](https://api.shippable.com/projects/5af6bf74e790f4070084a115/badge?branch=master)](https://app.shippable.com/github/OpenAPITools/openapi-generator)
 [![Windows Test](https://ci.appveyor.com/api/projects/status/github/openapitools/openapi-generator?branch=master&svg=true&passingText=Windows%20Test%20-%20OK&failingText=Windows%20Test%20-%20Fails)](https://ci.appveyor.com/project/WilliamCheng/openapi-generator-wh2wu)
 
+[`3.4.x`](https://github.com/OpenAPITools/openapi-generator/tree/3.4.x) branch: [![Build Status](https://img.shields.io/travis/OpenAPITools/openapi-generator/3.4.x.svg?label=Integration%20Test)](https://travis-ci.org/OpenAPITools/openapi-generator)
+[![Integration Test2](https://circleci.com/gh/OpenAPITools/openapi-generator/tree/3.4.x.svg?style=shield)](https://circleci.com/gh/OpenAPITools/openapi-generator)
+[![Run Status](https://api.shippable.com/projects/5af6bf74e790f4070084a115/badge?branch=3.4.x)](https://app.shippable.com/github/OpenAPITools/openapi-generator)
+[![Windows Test](https://ci.appveyor.com/api/projects/status/github/openapitools/openapi-generator?branch=3.4.x&svg=true&passingText=Windows%20Test%20-%20OK&failingText=Windows%20Test%20-%20Fails)](https://ci.appveyor.com/project/WilliamCheng/openapi-generator-wh2wu)
+
 [`4.0.x`](https://github.com/OpenAPITools/openapi-generator/tree/4.0.x) branch: [![Build Status](https://img.shields.io/travis/OpenAPITools/openapi-generator/4.0.x.svg?label=Integration%20Test)](https://travis-ci.org/OpenAPITools/openapi-generator)
 [![Integration Test2](https://circleci.com/gh/OpenAPITools/openapi-generator/tree/4.0.x.svg?style=shield)](https://circleci.com/gh/OpenAPITools/openapi-generator)
 [![Run Status](https://api.shippable.com/projects/5af6bf74e790f4070084a115/badge?branch=4.0.x)](https://app.shippable.com/github/OpenAPITools/openapi-generator)