Added `repl:assembly` and `repl:dist` tasks to the build.

[markhibberd]

You should be able to just run the following and drop straight into a repl with the current scoobi source:

./sbt "repl:dist" 
HADOOP_CONF_DIR=somewhere ./target/scoobi-repl-0.8.0-SNAPSHOT/scoobi

Basically the changes are:

• repl:assembly builds a fat jar as per what the old repl sub project did.
• repl:dist builds a directory, target/scoobi-repl-${version}, containing a runnable repl and tar balls up the directory at target/scoobi-repl-${version}
• this change removes the repl sub project
• I took some liberties with the shell script so just check what I did. Basically changes so it would work on bsd, osx and linux, and drop the version number from the jar it references (the repl:dist task creates a symlink for the general name from the versioned name)
• The code around creating the distribution is pretty funky and may require a revisit, yell if you want me to do it now.

[markhibberd]

I pushed an extra commit to let the script use HADOOP_CONF_DIR if it is set.