Exclude Precise from Packaging

Previously, the offline packaging build downloaded platform-specific
dependencies for Mountain Lion, Precise, and Trusty.  As Precise is no longer
a supported platform, this change removes it from that list, shrinking the
size of the offline packaged buildpack.

Author: nebhale

rakelib/package.rb

@@ -32,7 +32,7 @@ def self.version
 
   BUILDPACK_VERSION = JavaBuildpack::BuildpackVersion.new(false).freeze
 
-  PLATFORMS = %w(mountainlion precise trusty).freeze
+  PLATFORMS = %w(mountainlion trusty).freeze
 
   STAGING_DIR = "#{BUILD_DIR}/staging".freeze