Remove PHP 5.3 from Travis suite, updating minimum version requirement.

Since SilverStripe 4 isn't going to work on PHP 5.3, I have removed it from the Travis suite.

.travis.yml

@@ -37,8 +37,6 @@ matrix:
       env: DB=MYSQL
     - php: 5.4
       env: DB=MYSQL BEHAT_TEST=1
-    - php: 5.3
-      env: DB=MYSQL
     - php: 7.0
       env: DB=MYSQL
     - php: nightly

composer.json

@@ -16,7 +16,7 @@
 		}
 	],
 	"require": {
-		"php": ">=5.3.3",
+		"php": ">=5.4.0",
 		"composer/installers": "~1.0"
 	},
 	"require-dev": {

docs/en/00_Getting_Started/00_Server_Requirements.md

@@ -8,7 +8,7 @@ Our web-based [PHP installer](installation/) can check if you meet the requireme
 
 ## Web server software requirements
 
- * PHP 5.3.3+
+ * PHP 5.4+
  * We recommend using a PHP accelerator or opcode cache, such as [xcache](http://xcache.lighttpd.net/) or [WinCache](http://www.iis.net/download/wincacheforphp).
  * Allocate at least 48MB of memory to each PHP process. (SilverStripe can be resource hungry for some intensive operations.)
  * Required modules: dom, gd2, fileinfo, hash, iconv, mbstring, mysqli (or other database driver), session, simplexml, tokenizer, xml.