Add Coverage badge

Author: staticfloat

README.md

@@ -1,5 +1,6 @@
 # ObjectFile
 
 [![Build Status](https://travis-ci.org/staticfloat/ObjectFile.jl.svg?branch=master)](https://travis-ci.org/staticfloat/ObjectFile.jl)
+[![Coverage](http://codecov.io/github/staticfloat/ObjectFile.jl/coverage.svg?branch=master)](http://codecov.io/github/staticfloat/ObjectFile.jl?branch=master)
 
 This package provides basic functionality to read and analyze binary object files. It was written with ELF/MachO/COFF in mind, but should be easily adaptable to other object files as well.  While not originally intended as a package to enable the construction of a compiler/linker, the package authors welcome any and all efforts to extend the capabilities of this package toward synthesis of object files as well as the analysis of them.