Fix handling of Unicode characters ð, Å, å (#1157)
Fix handling of Unicode characters ð, Å, å (#1157)

* Fix double handling of ð (math maps to \eth, not special Unicode character)
* Remove Åå special math handling, thanks to #1125
xymostech/KaTeX,xymostech/KaTeX,xymostech/KaTeX,xymostech/KaTeX,Khan/KaTeX,xymostech/KaTeX,Khan/KaTeX,Khan/KaTeX