Improve install documentation (link to fedora official package)

fixes #21

Change-Id: I90d2f13a0a6595a2e29726659359962af39e1839
Reviewed-on: http://review.couchbase.org/89562
Reviewed-by: Sergey Avseyev <[email protected]>
Tested-by: Sergey Avseyev <[email protected]>

Author: remicollet

README.md

@@ -21,13 +21,27 @@ It supports 5.x and 7.x releases of PHP interpreter.
 The target system should have libcouchbase installed. Detailed guide and links to the most recent versions
 located here: https://developer.couchbase.com/server/other-products/release-notes-archives/c-sdk.
 
+### PECL
+
 Couchbase PHP client generally available through PECL: http://pecl.php.net/package/couchbase
 
 ```bash
 pecl install couchbase
 ```
 
-RPM packages available for Fedora 24-27 and RHEL 6-7 linux on https://rpms.remirepo.net/.
+### Binary packages
+
+RPM package for Fedora available in official repository, its name is [php-pecl-couchbase2](https://apps.fedoraproject.org/packages/php-pecl-couchbase2).
+
+```bash
+dnf install php-pecl-couchbase2
+```
+
+RPM package for RHEL and CentOS linux available on [Remi's repository](https://rpms.remirepo.net/).
+
+```bash
+yum install php-pecl-couchbase2
+```
 
 Additionally Windows builds available from [Release Notes and Archives](http://developer.couchbase.com/server/other-products/release-notes-archives/php-sdk) page.
 
@@ -38,6 +52,8 @@ brew tap homebrew/homebrew-php
 brew install php70-couchbase # or other version instead of 70 (PHP 7.0)
 ```
 
+### Build from sources
+
 If you are going to prepare patches, or just need to install the most recent
 version from git, make sure you have PHP development tools and headers
 installed, and run the following commands: