add note about not using spaces in plugin names
add note about not using spaces in plugin names

[#140115921]

Signed-off-by: Matthew Boedicker <bd646ec310948bf2f36146b5501a0018bf548d0d@pivotal.io>

simonleung8/cli,fujitsu-cf/cli,simonleung8/cli,fujitsu-cf/cli,simonleung8/cli,fujitsu-cf/cli