Expect [1] scripts filenames generally end in .exp, although the code
itself is actually in Tcl.  I find my self manually selecting Tcl quite
often, so I think it would be nice if Geany would recognize it direcly
as Tcl.

[1] http://expect.sourceforge.net/Signed-off-by: Simon Marchi <simon.marchi@polymtl.ca>