Create ISSUE_TEMPLATE.md (mlflow#11)

Create template for GitHub issues

ISSUE_TEMPLATE.md

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+### System information
+- **Have I written custom code (as opposed to using a stock example script provided in MLflow)**:
+- **OS Platform and Distribution (e.g., Linux Ubuntu 16.04)**:
+- **MLflow installed from (source or binary)**: 
+- **MLflow version (run ``python -c "from mlflow import version; print(version.version)"``)**:
+- **Python version**: 
+- **npm version (if running the dev UI):
+- **Exact command to reproduce**:
+
+### Describe the problem
+Describe the problem clearly here. Be sure to convey here why it's a bug in MLflow or a feature request.
+
+### Source code / logs
+Include any logs or source code that would be helpful to diagnose the problem. If including tracebacks,
+please include the full traceback. Large logs and files should be attached.
+Try to provide a reproducible test case that is the bare minimum necessary to generate the problem.