CodeSniffer coding standard for Observium

I'm attaching a patch to drop a PHP CodeSniffer coding standard into a contrib/phpcs/Observium/ directory. The only part of the path that matters is the Observium directory name. I think CodeSniffer uses it for a namespace when searching for Sniffs.

The standard was developed on CentOS 6 with the default PHP-CodeSniffer 1.4.5). It relies heavily on existing checks from the CodeSniffer distribution, but Ubuntu and other distros should have everything included.

To use the standard, do something like this:
`phpcs --standard=contrib/phpcs/Observium/ path/to/my.php`
`phpcs --standard=contrib/phpcs/Observium/ dir/path/`

There are two Observium error rules that I don't have implemented. They are noted at the top of ruleset.xml as a TODO comment. They have to do with blank lines after global statements and before a return statement.

I didn't write any Docs or Tests for the standard. See the ruleset and sniffs for documentation. Tests can come later if we find bugs in the sniffs.

And if you want to get crazy later, you can tie it into svn with a pre-commit hook.