message: Update build.rst
  c 'max_prepared_transactions=100' flag for postgres docker container
diff: @@ -339,7 +339,8 @@ Alternatively, you can run following command in the ``build`` folder
  -e POSTGRES_USER=postgres \
  -e POSTGRES_PASSWORD=mysecretpassword \
  -p 5432:5432 \
  - -d postgres:9.5
  + -d postgres:9.5 \
  + -c 'max_prepared_transactions=100'
  Building Iroha on Windows
  