ENH: Add support for continuous integration testing using CircleCI

This commit adds config file teaching CircleCI how to configure, build
and test the project.

The project will be tested using a docker container associated with
ITK v4.8.0.

If the container already exists on dockerhub, it will be pulled otherwise
CircleCI will fail.

This commit also update the README file adding the convenient CircleCI status
badge. Note that test results will also be submitted on CDash:

  http://slicer.cdash.org/index.php?project=SlicerExecutionModel

See PR #49

Co-authored-by: Matt McCormick <matt.mccormick@kitware.com>
Co-authored-by: Jean-Christophe Fillion-Robin <jchris.fillionr@kitware.com>

Author: 3 people

README.md

@@ -1,6 +1,8 @@
 SlicerExecutionModel
 ====================
 
+[![Circle CI](https://circleci.com/gh/Slicer/SlicerExecutionModel.svg?style=svg)](https://circleci.com/gh/Slicer/SlicerExecutionModel)
+
 Overview
 --------
 

circle.yml

@@ -0,0 +1,14 @@
+machine:
+  services:
+    - docker
+
+dependencies:
+  override:
+    - docker info
+    - docker pull slicer/slicerexecutionmodel:itk-v4.8.0_use_system_libraries-off
+
+test:
+  override:
+    - mkdir ~/SlicerExecutionModel-build
+    - docker run -v ~/SlicerExecutionModel:/usr/src/SlicerExecutionModel -v ~/SlicerExecutionModel-build:/usr/src/SlicerExecutionModel-build slicer/slicerexecutionmodel:itk-v4.8.0_use_system_libraries-off /usr/src/SlicerExecutionModel/test/Docker/test.sh
+