Sbt integration for users

Please read my comment on pull request #5 before reading the following =).

I updated the SBT part on the README and disabled the integrity check for dependencies in build.sbt. B2S repository is a bit crappy...SHA1 checksum is not valid for LWJGL 2.1 (needed by Slick2D 274, i don't know why).



Some thoughts : 

- You should either : 
    * Update Slick2D to its last revision because it includes LWJGL 2.9 instead of this old 2.1 (http://slick.ninjacave.com/). Or at least a more recent revision. The problem is it might be difficult because Slick2D developpers are using Ant instead of Maven. There is a project which aims providing a Maven build, seems to be active : https://github.com/nguillaumin/slick2d-maven/
    * Pull LWJGL 2.1 from B2S repository and push it into your Maven repository after regenerating the SHA1. So that you can get rid of B2S repository, and i think it would be a really good thing for you.

- LWJGL is now on Maven central, so you don't need the old http://adterrasperaspera.com/lwjgl any more. You just need to check the groupId and artifactId.

- You should change the "packaging" from "zip" to "jar" in Phys2D's pom.xml on your Maven Repo. Maven can deal with weird packaging like this one, and treat it as a jar, but SBT can't, he's looking for a zip and fails. Fortunately, SBT LWJGL Plugin takes care about this issue (he patches the pom just after downloading), so it's not really a problem for me, but it's never a good idea to keep potential bugs.



About the README commit : 

- About the first part (pulling out and publishing locally Scage), i tried first to specify your artifact (on your Maven repo') as a dependency but for an obscure reason the JVM crashed when i tried to run my sample project (maybe because i've a x64 OS ?). So i had to compile Scage by myself to be able to run the sample. I don't know yet where does this issue come from. I'll have a look later.

- For the second and third parts (build.sbt and project/plugins.sbt), i HAVE TO use the SBT LWJGL Plugin to get things work correctly. It's not really a problem (despite the config files are a bit more verbose) except that the plugin does not let me choose the LWJGL version. So, currently, it is using the 2.8.5 (better than the 2.7 before !). I know you are using the 2.8.2, so that it should be okay.



Thanks for reading =). Any comment will be appreciated.