871449 adding composer bubble style seperately

https://bugzilla.mozilla.org/show_bug.cgi?id=871449

I have tried the below two approaches

1) having common peep-bubble in mail.css
but ended up with many regressions, may be I did in wrong way.
so I left that approach

2) Tried with separate text-overflow:ellipsis;  styling for .cmp-peep-bubble  and added this class to the peep node along with .msg-peep-bubble.

I tested thoroughly in both composer and message reader screens.
If this approach is okay , please accept the patch.

Thanks.