abc.sh: enable _tar_FLAGS to be set automatically

Script now uses case statement to determine tar flags, rather than -a option
which was not FreeBSD compatible.
version bump 0.1.4 > 0.1.5
abc.sh: removed compression from rsync flags
Fix bug in delete function

function would not delete backups because pulling out the first 10 characters
created a string that always failed the date comparison

Signed-off-by: Andrew Turner <andrewjamesturner0@gmail.com>
version bump 0.1.5 > 0.1.6

Signed-off-by: Andrew Turner <andrewjamesturner0@gmail.com>