rework with syntax highlighting

Reworked the README to include syntax highlighting for sanity while reading, as well as a few posed changes for `uniformity`.
Don't let header fields clobber eachother

See: http://php.net/manual/en/function.header.php

2nd option, $replace, should be false if sending multiple headers with the same name.

The difference can be observed by editing index.php (the example index page) so that before `echo 'hello'` is a line: `flight::response()->cache(false);`
and editing Response.php so that before `exit($this->body)` is a line: `var_dump(headers_list());`

Before change:

`array (size=3)`
`0 => string 'Expires: Mon, 26 Jul 1997 05:00:00 GMT' (length=38)`
`1 => string 'Cache-Control: max-age=0' (length=24)`
`2 => string 'Pragma: no-cache' (length=16)`

After:

`array (size=5)`
`0 => string 'Expires: Mon, 26 Jul 1997 05:00:00 GMT' (length=38)`
`1 => string 'Cache-Control: no-store, no-cache, must-revalidate' (length=50)`
`2 => string 'Cache-Control: post-check=0, pre-check=0' (length=40)`
`3 => string 'Cache-Control: max-age=0' (length=24)`
`4 => string 'Pragma: no-cache' (length=16)`
Merge pull request #27 from kafene/master

Don't let header fields clobber eachother
Merge pull request #26 from Xanza/patch-1

rework with syntax highlighting
Fixed variable name typo in template/layout example.

This is also a typo on the http://flightphp.com/learn page.
Merge pull request #29 from magnetikonline/patch-1

Fixed variable name typo in template/layout example.
Updated readme.
Merge remote-tracking branch 'origin/master'
Added route passing functionality.
Changed header sizes.
Fixed issue with url pattern matching.
Fix line feeds.
Start proper versioning.
Fixed documentation
Merge pull request #44 from mateuszgachowski/master

Fixed documentation
Introduced new Engine class.

Core functionality has been moved to a namespaced Engine class. The
existing Flight class is now just a static pass-through to the Engine class.
Also fixed autoloading and initialization issues.
Merge remote-tracking branch 'origin/master'
Cleaned up initialization process.
Added example for new Engine class.
Fixed issue with 304 caching. Fixed PHP 5.3 compatibility.