文档来源： https://code.google.com/p/go-wiki/wiki/GoGetTools
被墙了，所以转在这个备用。
Installing Version Control Tools for go get
The go get fetching of source code is done by using one of the following tools expected to be found on your system:
svn - Subversion, download at: http://subversion.apache.org/packages.html
hg - Mercurial, download at http://mercurial.selenic.com/wiki/Download
git - Git, download at http://git-scm.com/downloads
bzr - Bazaar, download at http://wiki.bazaar.canonical.com/Download
git 安装时， 均是默认选项， 注意下面这项不是：
默认是第一项， 我们选择的是第二项。
hg – Mercurial 我安装的是：
TortoiseHg with Windows Explorer "shell" integration all-in-one installer with TortoiseHg 3.1.2 and Mercurial 3.1.2 (alternate download: Bitbucket)
