external links: remove blogs/newsletters/books sections (#469)

- there are countless good sysadmin resources of these types, maitaining a comprehensive list here would take too much time, out of scope
- the resources listed here are either too specific, or can easily be found by web search, or low-quality ("7 Proven Tips to Boost Your Passive Income from Affiliate Marketing"...)
- this leads to "spammy" pull requests/issues from people wanting to promote their own blog
- if someone wants to maintain a third-party list of good blogs/books/newsletters please make yourself known through the project issues

README.md

@@ -774,26 +774,8 @@ _See also: [awesome-selfhosted/Database Management](https://github.com/awesome-s
 
 ## External links
 
-Various resources, such as books, websites and articles, for improving your skills and knowledge.
-
-## Blogs
-
-- [Code as Craft](https://codeascraft.com/) - Etsy's Ops blog, lots of technical posts.
-- [DevOpsGuys](http://blog.devopsguys.com/) - Devops consultants who blog about operations.
-- [Rackspace Developers](https://developer.rackspace.com/blog/) - Slightly biased blog with lots of Devops Topics.
-- [RoseHosting Blog](https://www.rosehosting.com/blog/) - Linux tutorials for installing and configuring various software through the Linux command line. Guides and introductions to different Linux technologies and applications. Tips and tricks you can do via the Linux command line and more.
-
-## Books
-
-*Sysadmin related books.*
-
-- [The Linux Command Line](http://linuxcommand.org/tlcl.php) - A book about the Linux command line by William Shotts.
-
-
 ## Communities / Forums
 
-*For the social people.*
-
 - [ArsTechnica OpenForum](http://arstechnica.com/civis/) – IT Forum which is attached to a large news site.
 - [Reddit](https://www.reddit.com) - Really, really large bulletin board system.
   - [/r/Linux](https://www.reddit.com/r/linux) - News and information about Linux.
@@ -803,13 +785,6 @@ Various resources, such as books, websites and articles, for improving your skil
 - [StackExchange Network](https://stackexchange.com/sites#technology) – Q&A communities.
   - [Server Fault](https://serverfault.com/) – StackExchange community for system and network administrators.
 
-
-## Newsletters
-
-- [Servers for Hackers](https://serversforhackers.com/) - Newsletter for programmers who find themselves needing to know their way around a server.
-- [Web Operations Weekly](http://webopsweekly.com/) - A weekly newsletter on Web operations, infrastructure, performance, and tooling, from the browser down to the metal.
-
-
 ## Repositories
 
 *Software package repositories.*
@@ -822,11 +797,8 @@ Various resources, such as books, websites and articles, for improving your skil
 - [Remi](http://rpms.famillecollet.com/) - Repository with LAMP updated packages for RHEL/Centos/Fedora.
 - [Software Collections](https://www.softwarecollections.org) - Community Release of [Red Hat Software Collections](https://access.redhat.com/documentation/en/red-hat-software-collections/). Provides updated packages of Ruby, Python, etc. for CentOS/Scientific Linux 6.x.
 
-
 ## Websites
 
-*Useful sysadmin related websites.*
-
 - [ArchWiki](https://wiki.archlinux.org/) – Arch Linux Wiki which has really nice written articles valid for other distros.
 - [Gentoo Wiki](https://wiki.gentoo.org/) - Gentoo Linux Wiki with a lot in-detail description of Linux components.
 - [Awesome SysAdmin @ LibHunt](https://sysadmin.libhunt.com) - Your go-to SysAdmin Toolbox. Based on the list here.