"Die" is a bad approach to error handling

```
The converter calls die() if it can't read a spreadsheet. Throw an exception
instead so calling programs can deal with the failure. Patch is attached.

```

Original issue reported on code.google.com by `d...@cimpress.com` on 6 Jul 2010 at 7:17

Attachments:
- [patch.txt](https://storage.googleapis.com/google-code-attachments/php-excel-reader/issue-80/comment-0/patch.txt)

Start at the converter's spreadsheet-reading failure path and review the attached patch for the intended scope. Replace the direct die() failure with an exception that calling programs can handle, then verify that unreadable spreadsheets no longer terminate the caller unexpectedly.

Written by the indexing model from the issue text.