Adding CircleCI build

[sjurgemeyer]

Allow the repository to be built in CircleCI and deployed to bintray. This will require a few items to be set up once merged.

Create a package on Bintray:
Steps 1-4 of https://bintray.com/docs/usermanual/uploads/uploads_howdoiuploadmystufftobintray.html

Configure CircleCI:
Enable the build on circleci.com by clicking on 'Add Projects' and then 'Build Project' by this repo
In the settings for that project set the following environment variables
BINTRAY_URL - /bintray-user/bintray-repo/bintray-project e.g. sjurgemeyer/maven/twcs/
BINTRAY_USERNAME = your bintray username
BINTRAY_PASSWORD = your bintray API Key

This also adds the maven wrapper so the build will use a consistent version of maven.

[sjurgemeyer]

This uploads but does not automatically publish items to bintray. That can be done manually after the build completes, or line 30 of pom.xml can be updated to set publish=1

[jeffjirsa]

Thanks so much for this! It looks like TWCS may go upstream - if that happens, I'll focus my efforts there, and will probably close/shutter this repo. Let's hold on this momentarily.