(PHP 5.3+) Added "scanResource" method, and "scanLocalFile" now scans in a streaming manner

[TheOnlyMerlin]

If you would like any more information about my thinking, please let me know.

TLDR: Added ability to scan an arbitrary file or resource in a streaming manner, modified to work with PHP 5.3

What Was Changed

• Added public method: scanResource to scan a stream resource (e.g. returned from fopen())
• Updated public method: scanLocalFile to scan the specified file in a streaming manner
• Added protected method: _chunkStream, which allows you to apply a closure to chunks of a resource
• Added public method getSocket so that the chunked resources can access the internal socket
• Updated unit tests and README.md

  Decision Points

• 5.3 vs 5.4 - PHP 5.3 does not support using $this in closures, which breaks the use of _chunkStream (because it needs to access private / protected methods, ie access the socket). I would prefer using the 5.4 PR, but that involves potentially breaking changes (ie requiring PHP5.4).
• scanStream was not changed in order to avoid breaking any projects using this method. Strictly speaking, this does not scan a stream, it scans a string in chunks. If the project owner would like to change the method signature, I can update my PR.

[SenseException]

I close this PR after being inactive for over one year.