StGit 0.19 released

Thanks to Peter Grayson, a new StGit release is available. The main features:

• Python 3 support. StGit supports Python 2.6, 2.7, 3.3, 3.4, 3.5, 3.6, and 3.7. PyPy interpreters are also supported.
• Submodules are now ignored when checking if working tree is clean. Submodules are also not included by default when refreshing a patch.
• Config booleans are now parsed similarly to git-config.
• contrib/stgit.el is now licenced with GPLv2.
• Repair handling of emails with utf-8 bodies containing latin-1 characters. Also correctly decode email headers containing quoted encoded words.
• StGit’s version is now correct/available the release archive.
• Add continuous integration (travis-ci) and code coverage (coveralls) support.
• Many new test cases were added.