Strip newlines out of concatenated summaries.
Strip newlines out of concatenated summaries.

When posting a review using --guess-summary, we would concatenate all of the
summary lines, including newline characters. If one then tried to publish the
review as such, the email layer would freak out because there were newlines in
the subject header.

Fixes bug 1689

beol/rbtools,haosdent/rbtools,davidt/rbtools,halvorlu/rbtools,halvorlu/rbtools,davidt/rbtools,clach04/rbtools_0.4.1,reviewboard/rbtools,datjwu/rbtools,reviewboard/rbtools,datjwu/rbtools,davidt/rbtools,haosdent/rbtools,bcelary/rbtools,haosdent/rbtools,Khan/rbtools,beol/rbtools,clach04/rbtools,halvorlu/rbtools,beol/rbtools,datjwu/rbtools,1tush/rbtools,Khan/rbtools,reviewboard/rbtools