Increment to 3.0.0.

This is a massive update, so it's warranted. And many plugins will have
to be updated, though mostly because the packets themselves have 
changed.

ProtocolLib/pom.xml

@@ -2,7 +2,7 @@
   <modelVersion>4.0.0</modelVersion>
   <groupId>com.comphenix.protocol</groupId>
   <artifactId>ProtocolLib</artifactId>
-  <version>2.7.4-SNAPSHOT</version>
+  <version>3.0.0-SNAPSHOT</version>
   <packaging>jar</packaging>
   <description>Provides read/write access to the Minecraft protocol.</description>