Update readme for v3.4 release (vesoft-inc#250)

* Fix format

* Update README

README.md

@@ -7,7 +7,7 @@
 **IMPORTANT: Code of Nebula go client has been transferred from [nebula-clients](https://github.com/vesoft-inc/nebula-clients) to this repository(nebula-go), and new releases in the future will be published in this repository.
 Please update your go.mod and imports correspondingly.**
 
-Official Nebula Go client which communicates with the server using [fbthrift](https://github.com/facebook/fbthrift/). Currently the latest stable release is **[v3.3.0](https://github.com/vesoft-inc/nebula-go/tree/release-v3.3)**
+Official Nebula Go client which communicates with the server using [fbthrift](https://github.com/facebook/fbthrift/). Currently the latest stable release is **[v3.4.0](https://github.com/vesoft-inc/nebula-go/tree/release-v3.4)**
 
 The code in **master branch** will be updated to accommodate the nightly changes made in NebulaGraph.
 To Use the console with a stable release of NebulaGraph, please check the branches and use the corresponding version.
@@ -22,6 +22,7 @@ To Use the console with a stable release of NebulaGraph, please check the branch
 |   **[v3.1.x](https://github.com/vesoft-inc/nebula-go/tree/v3.1.0)**      |       3.1.x    |
 |   **[v3.2.x](https://github.com/vesoft-inc/nebula-go/tree/v3.2.0)**      |       3.1.x-3.2.x    |
 |   **[v3.3.x](https://github.com/vesoft-inc/nebula-go/tree/v3.3.0)**      |       3.1.x-3.3.x    |
+|   **[v3.4.x](https://github.com/vesoft-inc/nebula-go/tree/v3.4.0)**      |       3.1.x-3.4.x    |
 |   **[master](https://github.com/vesoft-inc/nebula-go/tree/master)**     |       3.x-nightly |
 
 Please be careful not to modify the files in the nebula directory, these codes were all generated by fbthrift.
@@ -37,7 +38,7 @@ $ go get -u -v github.com/vesoft-inc/nebula-go/v3@master
 You can specify the version of Nebula-go by substituting `<tag>` in `$ go get -u -v github.com/vesoft-inc/nebula-go@<tag>`.
 For example:
 
-  for v3: `$ go get -u -v github.com/vesoft-inc/nebula-go/v3@v3.3.0`
+  for v3: `$ go get -u -v github.com/vesoft-inc/nebula-go/v3@v3.4.0`
 
   for v2: `$ go get -u -v github.com/vesoft-inc/nebula-go/[email protected]`