v16

Several updates:

• Quiets various type warnings
• Adds some helpful object API calls
• Fixes cmp_read_ufix expecting negative, not positive fixints
• Adds MessagePack v4 compatibility functions
• - Puts cmp_read/_write_float/_double functions beneath cmp_write_decimal
• Adds a code of conduct
• Updates copyrights
• Fixes issue where floats were occasionally corrupted on little-endian machines