Updating client to be compliant with RFC 2616: case-insensitive headers

[douglasmiller]

According to section 4.2 of RFC 2616:

Each header field consists of a name followed by a colon (":") and the field value. Field names are case-insensitive.

This update will make the client treat headers in a case-insensitive manner.

[dbrudner]

ref: refs/heads/2-3-headers
PHP 5.3.29 (cli) (built: Oct  9 2014 00:21:49) 
Copyright (c) 1997-2014 The PHP Group
Zend Engine v2.3.0, Copyright (c) 1998-2014 Zend Technologies
PHPUnit 4.2.6 by Sebastian Bergmann.

..............................................................

Time: 1.86 seconds, Memory: 10.00MB

OK (62 tests, 198 assertions)

[dbrudner]

ref: refs/heads/2-3-headers
PHP 5.4.45 (cli) (built: Dec  5 2015 08:26:46) 
Copyright (c) 1997-2014 The PHP Group
Zend Engine v2.4.0, Copyright (c) 1998-2014 Zend Technologies
PHPUnit 4.2.6 by Sebastian Bergmann.

..............................................................

Time: 1.05 seconds, Memory: 6.50MB

OK (62 tests, 198 assertions)

[dbrudner]

ref: refs/heads/2-3-headers
PHP 5.5.38 (cli) (built: Aug 10 2016 20:52:31) 
Copyright (c) 1997-2015 The PHP Group
Zend Engine v2.5.0, Copyright (c) 1998-2015 Zend Technologies
PHPUnit 4.2.6 by Sebastian Bergmann.

..............................................................

Time: 1.1 seconds, Memory: 6.75MB

OK (62 tests, 198 assertions)