Adds the IntelliJ project directory to .gitignore.
Adds the IntelliJ project directory to .gitignore.

I'm trying to move away from Netbeans, so I thought
I should ignore this instead of accidentally adding it later on

Signed-off-by: Cruz Julian Bishop <2ec049a14d87a31aea1a3d03a4724ab112720c17@gmail.com>

CliffYuan/netty,KeyNexus/netty,KeyNexus/netty,CliffYuan/netty