Releasing Satpy

checkout master
pull from repo
run the unittests
run loghub and update the CHANGELOG.md file:
```
loghub pytroll/satpy --token $LOGHUB_GITHUB_TOKEN -st v<previous version> -plg bug "Bugs fixed" -plg enhancement "Features added" -plg documentation "Documentation changes" -plg backwards-incompatibility "Backward incompatible changes" -plg refactor "Refactoring"
```
This uses a LOGHUB_GITHUB_TOKEN environment variable. This must be created on GitHub and it is recommended that you add it to your .bashrc or .bash_profile or equivalent.

This command will create a CHANGELOG.temp file which need to be added to the top of the CHANGLOG.md file. The same content is also printed to terminal, so that can be copy-pasted, too. Remember to update also the version number to the same given in step 5. Don't forget to commit CHANGELOG.md!
Create a tag with the new version number, starting with a 'v', eg:
```
git tag -a v<new version> -m "Version <new version>"
```
For example if the previous tag was v0.9.0 and the new release is a patch release, do:
```
git tag -a v0.9.1 -m "Version 0.9.1"
```
See semver.org on how to write a version number.
push changes to github git push --follow-tags
Verify travis tests passed and deployed sdist and wheel to PyPI