Returns the string, first removing all
whitespace on both ends of the string, and then changing remaining
consecutive whitespace groups into one space each.
Examples:
%{ Multi-line
string }.squish# => "Multi-line string"" foo bar \n\t boo".squish# => "foo bar boo"
# File activesupport/lib/active_support/core_ext/string/filters.rb, line 12
def squish
dup.squish!
end