cosmetic and corner cases fixes to install.sh (#894)
cosmetic and corner cases fixes to install.sh (#894)

* Quote $PWD so that directories with spaces work
* Replace "\n" in echo with empty echo commands
* Add check if sudo command is available. Don't use sudo if not available
* Check that creating popper file is successful. If we don’t have write
  permissions in the folder, there must not be a
  success message, but an error.
systemslab/popper,systemslab/popper