missing utils/README.md

[csantanapr]

The installed actions for utils package are not documented

$ wsk package get /whisk.system/utils --summary
package /whisk.system/utils: Building blocks that format and assemble data
 action /whisk.system/utils/date: Current date and time
 action /whisk.system/utils/head: Extract prefix of an array
   (parameters: lines, num)
 action /whisk.system/utils/split: Split a string into an array
   (parameters: payload, separator)
 action /whisk.system/utils/sort: Sorts an array
   (parameters: lines)
 action /whisk.system/utils/echo: Returns the input
   (parameters: payload)
 action /whisk.system/utils/cat: Concatenates input into a string
   (parameters: lines)