README: More consistent formatting with other Go packages. (gregjones#68)

Remove the redundant "A Transport for Go's http.Client that will
cache responses according to the HTTP RFC" sentence. The next
paragraph says something similar. This sentence can already be
found in the repository description (one liner).

It's very common to find a godoc.org link in the form of a badge in
most Go package repository READMEs. Therefore, it's more recognizable
and easier to click the link. I think we should use the badge to be
friendlier to users, and remove the superseded plain text link.

Move License note into its own section at the bottom. This is a more
common location. GitHub already detects and displays the license
prominently in top right corner, and there is a LICENSE file in the repo,
so it makes sense to place Cache Backends section higher up.

Author: dmitshur

README.md

@@ -1,19 +1,13 @@
 httpcache
 =========
 
-[![Build Status](https://travis-ci.org/gregjones/httpcache.svg?branch=master)](https://travis-ci.org/gregjones/httpcache)
-
-A Transport for Go's http.Client that will cache responses according to the HTTP RFC
+[![Build Status](https://travis-ci.org/gregjones/httpcache.svg?branch=master)](https://travis-ci.org/gregjones/httpcache) [![GoDoc](https://godoc.org/github.com/gregjones/httpcache?status.svg)](https://godoc.org/github.com/gregjones/httpcache)
 
 Package httpcache provides a http.RoundTripper implementation that works as a mostly RFC-compliant cache for http responses.
 
 It is only suitable for use as a 'private' cache (i.e. for a web-browser or an API-client and not for a shared proxy).
 
-**Documentation:** http://godoc.org/github.com/gregjones/httpcache
-
-**License:** MIT (see LICENSE.txt)
-
-Cache backends
+Cache Backends
 --------------
 
 - The built-in 'memory' cache stores responses in an in-memory map.
@@ -23,3 +17,8 @@ Cache backends
 - [`github.com/gregjones/httpcache/leveldbcache`](https://github.com/gregjones/httpcache/tree/master/leveldbcache) provides a filesystem-backed cache using [leveldb](https://github.com/syndtr/goleveldb/leveldb).
 - [`github.com/die-net/lrucache`](https://github.com/die-net/lrucache) provides an in-memory cache that will evict least-recently used entries.
 - [`github.com/die-net/lrucache/twotier`](https://github.com/die-net/lrucache/tree/master/twotier) allows caches to be combined, for example to use lrucache above with a persistent disk-cache.
+
+License
+-------
+
+-	[MIT License](LICENSE.txt)