Modify SVG parsing

Glyph ids are now parsed from the svg element attribute instead of the
path element to accomodate glyphs with multiple paths.
St. Gallen neume drawing

Created custom SVG glyphs for St. Gallen manuscript in adobe
illustrator and exported each to SVG, which is then parsed by Neon.js as
independent glyphs. Created Neon.js drawing code for the fundamental
glyphs in St. Gallen and it displays. Need to think about how to set the
global scale of glyphs. With staffed neumes, the global scale could be
set by comparing the size of the SVG to the distance between staff
lines.