Release, versioning and continous integration

1. We are following the [semantic versioning scheme](https://semver.org/) (i.e., X.Y.Z) , which means every hotfix will bump the version number to X.Y.(Z+1).
2. To support it, we need continuous integration which tracks the master branch to update the version number and generate the conda packages.
3. For updates to the dev branch, we also need the continuous integration tool to run the test and generate the nightly builds (conda packages).
4. Currently, we have Travis (for CPU) and Jenkins (CPU). They need to be updated to support 1, 2 and 3.