Update README markdown in according with CommonMark (closes #165)

README.md

@@ -1,10 +1,10 @@
 # referer-parser node.js (JavaScript) library
 
-This is the node.js (JavaScript) implementation of [referer-parser] [referer-parser], the library for extracting search marketing data from referer _(sic)_ URLs.
+This is the node.js (JavaScript) implementation of [referer-parser][referer-parser], the library for extracting search marketing data from referer _(sic)_ URLs.
 
-The implementation uses the shared 'database' of known referers found in [`referers.yml`] [referers-yml]
+The implementation uses the shared 'database' of known referers found in [`referers.yml`][referers-yml]
 
-The Javascript version of referer-parser is maintained by [Martin Katrenik] [mkatrenik].
+The Javascript version of referer-parser is maintained by [Martin Katrenik][mkatrenik].
 
 ## Installation
 
@@ -59,7 +59,7 @@ console.log(r.uri)                // result of require('url').parse(...)
 
 The referer-parser node.js (JavaScript) library is copyright 2013 Martin Katrenik.
 
-Licensed under the [Apache License, Version 2.0] [license] (the "License");
+Licensed under the [Apache License, Version 2.0][license] (the "License");
 you may not use this software except in compliance with the License.
 
 Unless required by applicable law or agreed to in writing, software