Update parser.js

Add support to catch attributes from symbol nodes.
This is a quick hack.
To have full support symbol should managed as defs and then copied as g, without display attribute.
But before adding tons of code, let's just make it work.
Update .travis.yml
Update parser.js

This was missing.
Now if width and height get parse correctly.
They were even before but if it was  width 18pt ( so 18 * 1.33 pixels ) and wievbox was 18, before no scaling was calculated.
Merge pull request #1574 from asturur/tag-symbol

Tag symbol