Release 0.8.7 (stable)

Major changes in 0.8.7

This is a minor security update, matching the behaviour on master
where we avoid ever creating setuid files or world-writable
directories. However, the fix is more localized and does not
require a new ostree.

Changes:

• After pulling from a remote, always verify that the staged
  new files and directories have safe permissions.
• Ensure ~/.local/share/flatpak is not readable to other users, to
  avoid anyone ever seeing possibly world-writeable directories
  therein.
• Fix double-setting a error in case of errors when pulling
• Fix timeout in testcase

$ sha256sum flatpak-0.8.7.tar.xz 
ddd2b1d5b291b55a12bee1ef802d2e36ca7c830e2164d38996fa62460196f311  flatpak-0.8.7.tar.xz