yaml exception with example code in README

[paolini]

In REAMDE.md you suggest to add these line to serverless.yml:

plugins:
  - serverless-client-s3
 custom:
   client:
     bucketName: serverless-client-bucketname

however this seems not to be valid yml. When executing serverless client deploy I get the following YAML exception:

  bad indentation of a mapping entry in "/Users/paolini/notes/serverless.yml" at line 59, column 2:
     custom:
     ^