Clean up old files, fix crashes, and fix font name issues

See #6 and #7.

Updated to include OS/2 metrics

Courtesy of #5 Quentin Renard

Applied all outstanding PRs from golang/freetype, various other fixes

Now has a go.mod, version 1.0.1.

• Rasterizer has UseNonZeroWinding = true to deal with overlapping paths
• GlyphAdvance ok returns false if rune is not specifically supported (index = 0)
• PR golang#70: does a better job of decoding utf16
• PR golang#86: round to nearest 26.6 fixed point
• PR golang#88: prefer full/UCS4 sub-tables over BMP/UCS2 ones