\u2018 includes a whitespace character under Mac OS X
As it turns out the problem was an option that I had set in iTerm2.  When you have the following option set for your iTerm2 profile, \u2018 is interpreted as an ambiguous-width char and so is considered to be double-width, but since it isn't an double-width character, such as a kanji, a space gets appended to it.  

Just make sure that you have the following option unchecked: