allow long names in titles to break

Until now, a `~` (non breaking space) connects first
and last name in the cv title. This prevents long
names to break correctly. This commit replaces the space
with `\ `, a space that allows breaking.

Fixes #220

moderncvheadi.sty

@@ -120,7 +120,7 @@
     \begin{minipage}[b]{\makecvheadnamewidth}%
       \if@left\raggedright\fi%
       \if@right\raggedleft\fi%
-      \firstnamestyle{\@firstname~}\lastnamestyle{\@lastname}%
+      \firstnamestyle{\@firstname\ }\lastnamestyle{\@lastname}%
       \ifthenelse{\equal{\@title}{}}{}{\\[1.25em]\titlestyle{\@title}}%
     \end{minipage}}%
   % raise boxes if top option is set