Return java exit code from python jgo
Return java exit code from python jgo

Example success code:
```
$ jgo -Xmx1g org.scijava:parsington 1+3; echo $?
4
0
```

Example failure code:
```
$ jgo -Xmx1y org.scijava:parsington 1+3; echo $?
Invalid maximum heap size: -Xmx1y
Error: Could not create the Java Virtual Machine.
Error: A fatal exception has occurred. Program will exit.
ERROR 2018-12-16 13:16:50,926: Error in `/usr/bin/java -cp /home/hanslovskyp/.jgo/org/scijava/parsington/RELEASE/* -Xmx1y org.scijava.parse.Main 1+3': 1
usage: jgo [-v] [-u] [-U] [-m] [--ignore-jgorc] [--link-type type] [--additional-jars jar [jar ...]] [--additional-endpoints endpoint [endpoint ...]] [JVM_OPTIONS [JVM_OPTIONS ...]] <endpoint> [main-args]

Run Java main class from maven coordinates.

optional arguments:
  -h, --help            show this help message and exit
  -v, --verbose         verbose mode flag
  -u, --update-cache    update/regenerate cached environment
  -U, --force-update    force update from remote Maven repositories (implies -u)
  -m, --manage-dependencies
                        use endpoints for dependency management (see "Details" below)
  -r REPOSITORY [REPOSITORY ...], --repository REPOSITORY [REPOSITORY ...]
                        Add additional maven repository (key=url format)
  -a ADDITIONAL_JARS [ADDITIONAL_JARS ...], --additional-jars ADDITIONAL_JARS [ADDITIONAL_JARS ...]
                        Add additional jars to classpath
  --additional-endpoints ADDITIONAL_ENDPOINTS [ADDITIONAL_ENDPOINTS ...]
                        Add additional endpoints
  --ignore-jgorc        Ignore ~/.jgorc
  --link-type {hard,soft,copy,auto}
                        How to link from local maven repository into jgo cache. Defaults to the `links' setting in ~/.jrunrc or 'auto' if not specified.

The endpoint should have one of the following formats:

- groupId:artifactId
- groupId:artifactId:version
- groupId:artifactId:mainClass
- groupId:artifactId:version:mainClass
- groupId:artifactId:version:classifier:mainClass

If version is omitted, then RELEASE is used.
If mainClass is omitted, it is auto-detected.
You can also write part of a class beginning with an @ sign,
and it will be auto-completed.
1
```

ctrueden/jrun,ctrueden/jrun