Update and enable TravisCI for community edition

[emxsys]

Update .travis.yml and enable TravisCI for the WorldWindEarth organization.

• [X] Activate TravisCI for WorldWindEarth/WorldWindJava
• [x] Update .travis.yml to publish API docs
• [x] Update .travis.yml to publish releases

[emxsys]

• Progress: activated TravisCI for WorldWindJava (https://travis-ci.com/WorldWindEarth/WorldWindJava)
• Next step: Update .travis.yml

[emxsys]

The .travis.yml deploy step was re-enabled after being commented out by the NASA suspension activities. The develop branch's javadoc is now published at https://worldwind.earth/WorldWindJava as can be seen in the following log snippet. A tagged release will generate a CHANGELOG.md that is deployed to the tagged release assets.

Travis log snippet

Preparing deploy
Deploying application
Initialized empty Git repository in /tmp/d20190411-6288-7krhyo/work/.git/
Switched to a new branch 'gh-pages'
cd -
cd /tmp/d20190411-6288-7krhyo/work
commit d0caf77194a91401333169907d8eba25c8bbb1b0
Author: Deployment Bot (from Travis CI) <deploy@travis-ci.org>
Date:   Thu Apr 11 13:49:40 2019 +0000
    Deploy WorldWindEarth/WorldWindJava to github.com/WorldWindEarth/WorldWindJava.git:gh-pages
 allclasses-frame.html                           |  1899 ++
 allclasses-noframe.html                         |  1899 ++
 constant-values.html                            | 23613 ++++++++++++++++++++++
 gov/nasa/worldwind/AbstractSceneController.html |  1902 ++
 gov/nasa/worldwind/BasicFactory.html            |   482 +
 gov/nasa/worldwind/BasicModel.html              |   610 +
 gov/nasa/worldwind/BasicSceneController.html    |   448 +
 gov/nasa/worldwind/Configuration.html           |   969 +
 gov/nasa/worldwind/Disposable.html              |   232 +
 gov/nasa/worldwind/Exportable.html              |   374 +
 ...
 4382 files changed, 1771446 insertions(+)
cd -