str-slice is returning the wrong value when $start-at is 1 and $end-at is 0 #760
Description
Seems like str-slice is returning the wrong value when $start-at is 1 and $end-at is 0 in libsass:
ruby-sass: str-slice("abcd", 1, 0); => ""
ruby-sass: str-slice("abcd", 2, 0); => ""
libsass: str-slice("abcd", 1, 0); => "a"
libsass: str-slice("abcd", 2, 0); => ""