Merge cells does not work with sheet names

Problem/Motivation

The merge cells option (merge_cells) considers sheet indices and not sheet names.

Steps to reproduce

Use any sheet name in the merge_cells option.
array('merge_cells' => array(
'Worksheet 1' => array(
'A1:C1',
'D1:G1',
),
))

Proposed resolution

Update the file phpexcel.inc.
Replace the line 142 :
$sheet = $xls->setActiveSheetIndex($sheet_name);
with :
$sheet = $xls->setActiveSheetIndexByName($sheet_name);

Remaining tasks

No more tasks.

User interface changes

No change.

API changes

No change.

Data model changes

No change.