Delete CNAME in Master Branch

CNAME is mainly used for custom domain with Github Pages. CNAME should
be put in the root of Master branch ONLY when the repository is a `User
Page Site` like `username.github.io`. Otherwise, it should be in the
root of `gh-pages` Branch.

This file may lead a misunderstanding of master branch for the freshers.
Merge pull request #1192 from wh1100717/master

Delete CNAME in Master Branch
Update: realpath method in util-path.js

1. DOUBLE_DOT_RE will match `a/b/c//../d` path correctly only if
replace `//` with `/` first
2.  `a///b/c` should be the path `a/b/c`
UPDATE: match multi slashes, not only double

Replace DOUBLE_SLASH_RE with MULTI_SLASH_RE. Now path like
`a////b////c` will be parsed to `a/b/c`correctly.
Merge pull request #1193 from wh1100717/master

Update: realpath method in util-path.js