Show sass file on the top of backtrace

[k0kubun]

When SyntaxError is raised, I want to see the broken sass file on error page. This is implemented in Sass::SyntaxError too.
Since we can know filename and lineno only from message, I implemented it by parsing it.

Screen shot

before

after

[k0kubun]

@bolandrm How do you think about this? Is there any blocker to merge? I want this patch to find what is wrong easily in development.

[bolandrm]

It looks good, no blockers. I just need to get some time to review and test it and then I will merge.

[k0kubun]

Thank you for your comment! I'm looking forward to being reviewed.

[bolandrm]

Sorry for the delay, I'll merge this in when I do the next update for libsass 3.3.6.

[bolandrm]

Hey, I did merge this in, but I made some changes so that we're using the filename and line number information for libsass.

73397b6

it's working in my application, but let me know if you have any issues. thanks for the contribution!

[k0kubun]

Hi. First of all, thank you for merging this PR! I confirmed your changes and changed my application to use sassc-ruby v1.10.0. I tried some invalid scss and it worked fine. I'll report an issue if I find.