sj-feature: set tracked branch (#156)

Make sure to set the tracked branch when creating features
so that `sj up` works as expected.

Signed-off-by: Phil Dibowitz <phil@ipom.com>

lib/sugarjar/commands.rb

@@ -50,6 +50,7 @@ def feature(name, base = nil)
         git('fetch', base_pieces[0]) if base_pieces.length > 1
       end
       git('checkout', '-b', name, base)
+      git('branch', '-u', base)
       SugarJar::Log.info(
         "Created feature branch #{color(name, :green)} based on " +
         color(base, :green),