4.You should try follow run this.
rm -rf "/usr/local/Homebrew/Library/Taps/homebrew/homebrew-core"
5.When no.4 is done run this
brew tap homebrew/core
For me, this one worked without the sudo access.
ruby -e "$(curl -fsSL https://raw.githubusercontent.com/Homebrew/install/master/install)"
For more reference, please followhttps://gist.github.com/mxcl/323731