Fix for issue #9

xmlrpc_decode() return values aren't consistent across php versions. In some versions of php it will return a string; in 5.5.11 it returns null on a successful pingback response. This changes fixes that issue.
Add ability to set CURL proxy string
Also look for <a> tags with rel=webmention
Replacing deprecated preg modifier

The /e modifier in preg_match is deprecated for security reasons. This patch replaces it with an equivalent use of preg_replace_callback.
update references to webmention.io
Merge pull request #11 from mapkyca/proxy

Add ability to set CURL proxy string
Merge pull request #10 from marcusjfloyd/patch-1

Fix for issue #9
Merge pull request #12 from benwerd/patch-1

Replacing deprecated preg modifier
Update README.md