StringGroovyMethods has many issue:
1) Inefficient converting CharSequence to String. If do not convert, the method of CharSequence wiil twice faster.
2) IOGroovyMethods.readLines is slow, do not use it. readLines use a closue!
3) the methods of center/denormalize/expand/pad/strip are Inefficient, there is no need creat so many StringBuilders
I'll fix this (on github) in a few days. Please help me check and merge it.