Update README.md

Update the json format of session for redis, there is an error in that json string
Update README.md

Update the json format of session for file, redis, mysql, there are errors in these json string, after `ProviderConfig` params.
Update README.md

Update the json format of session for file, redis, mysql, cookie, there are errors in these json string, such as after the param `ProviderConfig` and there is a lost of `"` in the line 61 of the `gclifetime`.
Merge pull request #591 from luosangnanka/master

Update Session package README.md
Merge branch 'master' of https://github.com/astaxie/beego