README is not consistant on the "sed" command

[sago007]

According to the README's "Security" section "sed" is not enabled by default.
However in the go version "sed" is now enabled by default.

It might not be a big deal as people that are granted access to Tailon are usually highly privileged anyway. It could still be a nasty surprise to some. Especially when upgrading from the python version.

Tested on release 1.1.0