Don't expect column number to always exists

[kjg]

I'm running some node code on apigee which uses rhino under the hood as the javascript engine.

Unfortunately Rhino does not include column numbers in their stack traces which currently causes stack trace parsing with this module to fail.

I've filed the following Issues:

• Stacktraces don't include the column number mozilla/rhino#304
• Stacktraces don't include the column number like node stacktraces do apigee/trireme#153

but I'm not counting on anything happening there.

This PR make the presence of a column number in the stack trace optional to support runtimes that don't output a column number.

[felixge]

This module was meant to only deal with v8/node stack traces, so I'm somewhat hesitant to add support for more engines. Your patch looks minimally invasive, so I think it's probably fine.

Anyway, if you can confirm that all other tests are still passing, I'll go ahead and merge.

[kjg]

Thanks for being so willing to accept this change!

I ran into some failures on master before making my changes. They all seem to be related to specific lines being at a different level in the stack than what the test is expecting. I'm assuming this has to do with the specific version of node and other environment differences with my setup. However as far as I could tell, the new test I'm adding failed before the code change and passes after, and all the other tests that were passing in master are still passing in this branch.

[felixge]

@kjg ok. Yeah, unfortunately this repo never got hooked up to travis or similar, so I'm not sure when stuff started to break. Anyway, thx for the patch, I just merged it in.

[kjg]

Would you mind publishing a new version to npm? Thanks!

[felixge]

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