Specifying the sbt version as 0.12.4 in order to work correctly with my 0.13 version
Got this working for 0.12/0.13, but won't work for 0.13 folks who are using xsbt-web-plugin 0.9
This change appears to make 0.13 w/ xsbt-web-plugin 0.9.0 happy, and still compiles for 0.12