[glyph] add remaining d3 symbols

[hshoff]

• adds support for the missing d3 symbols from d3-shape
• <GlyphDot /> should be considered deprecated in favor of <GlyphCircle /> for a consistent api across all Glyphs, but I'll keep GlyphDot around just in case folks are already using it as legacy

<GlyphCircle />

<GlyphSquare />

<GlyphWye />

<GlyphTriangle />

<GlyphStar />

<GlyphCross />

[coveralls]

Coverage decreased (-0.7%) to 26.758% when pulling c51e7e6 on harry-glyphs into 8c96326 on master.

[coveralls]

Coverage decreased (-0.7%) to 26.758% when pulling c51e7e6 on harry-glyphs into 8c96326 on master.

[hshoff]

adding glyphs in the custom legend demo

[coveralls]

Coverage decreased (-0.7%) to 26.758% when pulling ef63e98 on harry-glyphs into 8c96326 on master.