Remove bitbucket.org/zombiezen/yaml package.

Package has been last updated in early 2013. The description says it implements a YAML 1.2 parser, but as we've learned at https://github.com/shurcooL/markdownfmt/issues/11#issuecomment-54249637, it has high level parsing functionality completely unimplemented and marked as TODO.
Add Distributed Systems section
Update README.md

Added heka, godropbox and vitess
Add "CSS Preprocessors" category & "gcss" package
Added Snapchat to third party packages
Added rrdaclient, wrapper for statdns.com API. DNS queries over HTTP
Merge pull request #181 from yosssi/patch-2

Add "CSS Preprocessors" category & "gcss" package
Merge pull request #182 from jamieomatthews/patch-1

Added Snapchat to third party packages
Merge pull request #180 from kpashka/master

Added heka, godropbox and vitess
Merge pull request #178 from fromYukki/master

PHP Serialize/Unserialize and session encode/decode functions
Merge pull request #177 from avelino/remove-inactive-unfinished-package

Remove bitbucket.org/zombiezen/yaml package.
Merge pull request #183 from Omie/rrdaclient

Added rrdaclient
Merge pull request #179 from otoolep/ds

Add Distributed Systems section