[skip CI] add badges to README, rename to markdown

README → README.md

+[![Build Status](https://img.shields.io/travis/google/glog/master.svg?label=Travis)](https://travis-ci.org/google/glog/builds)
+[![Grunt status](https://img.shields.io/appveyor/ci/google/glog/master.svg?label=Appveyor)](https://ci.appveyor.com/project/google/glog/history)
+
 This repository contains a C++ implementation of the Google logging
 module.  Documentation for the implementation is in doc/.
 
 See INSTALL for (generic) installation instructions for C++: basically
-   ./autogen.sh && ./configure && make && make install
+```sh
+./autogen.sh && ./configure && make && make install
+```