add Largest Rectangle .. , max-depth-bt(recursive method)
Merge branch 'master' of https://github.com/staticor/Leetcode

* 'master' of https://github.com/staticor/Leetcode:
  add timus code, longlonggo, use ruby mainly

n updated upstream into a topic branch.
#
# Lines starting with '#' will be ignored, and an empty message aborts
# the commit.