`curl` should ignore `gnutls` and `librtmp`
Skip building Perl extensions that tend to link to system libs
Update to curl 7.36.0

This version fixes a number of important security vulnerabilities:

* libcurl wrong re-use of connections - http://curl.haxx.se/docs/adv_20140326A.html
* libcurl IP address wildcard certificate validation - http://curl.haxx.se/docs/adv_20140326B.html
* libcurl not verifying certs for TLS to IP address / Darwinssl - http://curl.haxx.se/docs/adv_20140326C.html
* libcurl not verifying certs for TLS to IP address / Winssl - http://curl.haxx.se/docs/adv_20140326D.html
Ensure nokogiri links against embedded zlib.
Use short versions of `mkmf` generated configure flags

`dir_config('foo')` sets up the following configure flags:

  --with-foo-dir
  --with-foo-include
  --with-foo-lib

More info at:

http://ruby-doc.org/stdlib-1.9.3/libdoc/mkmf/rdoc/Object.html#method-i-dir_config
Bump nokogiri's default_version to 1.6.1
Merge pull request #154 from opscode/schisamo/health-check-fixes

Health Check Fixes