Error building the image

I have tried to run the server and this is what I get.

```
...
Step 10 : WORKDIR lib/CoreNLP
---> Running in 50baef05f7ca
---> 053e341bb39e
Removing intermediate container 50baef05f7ca
Step 11 : RUN gradle build
---> Running in 4912791f7967

FAILURE: Build failed with an exception.

* What went wrong:
Task 'build' not found in root project 'CoreNLP'.

* Try:
Run gradle tasks to get a list of available tasks. Run with --stacktrace option to get the stack trace. Run with --info or --debug option to get more log output.

BUILD FAILED

Total time: 2.272 secs
The command '/bin/sh -c gradle build' returned a non-zero code: 1
```

This is what I tried:

``` bash
git clone https://github.com/akiomik/stanford-corenlp-server.git
cd stanford-corenlp-server
git submodule init
git submodule update
docker build -t akiomik/stanford-corenlp-server .
```

Any ideas?