Update changelog and bump version to v1.50

Signed-off-by: Kevin Cernekee <cernekee@gmail.com>
README: Convert to markdown format and update content

Signed-off-by: Kevin Cernekee <cernekee@gmail.com>
build-debian: Import latest version from stoken repo

Signed-off-by: Kevin Cernekee <cernekee@gmail.com>
release.sh: Import latest version from stoken repo

Signed-off-by: Kevin Cernekee <cernekee@gmail.com>
Rename debian -> ppa

Debian does not like it[1] when upstream packages include a debian/
directory, as it may conflict with packaging efforts.  So we will call
ours "ppa" instead.

[1] https://wiki.debian.org/UpstreamGuide#Pristine_Upstream_Source

Signed-off-by: Kevin Cernekee <cernekee@gmail.com>