Update README.md

Merge pull request json-iterator#170 from olegshaldybin/marshal-enum-…

…pointer

Fix custom marshaler for enum types

json-iterator#153 fix invalid utf8 using same implementation as the s…

…tandard library

json-iterator#135 verify 1e1 and 1.0e1 is handled same as std

cut 0.9.18

fix unicode and escape

json-iterator#69 fix unicode support

fix anonymous fields

json-iterator#54 support sort map keys

json-iterator#34 implement NewEncoder