Add curl package dependency

packages/dropbox_uploader.rb

@@ -7,6 +7,8 @@ class Dropbox_uploader < Package
   source_url 'https://github.com/andreafabrizi/Dropbox-Uploader/archive/1.0.tar.gz'
   source_sha256 '8c9be8bd38fb3b0f0b4d1a863132ad38c8299ac62ecfbd1e818addf32b48d84c'
 
+  depends_on 'curl'
+
   def self.install
     system "sed -i 's,dropbox_uploader.sh,dropbox_uploader,g' dropShell.sh"
     system "chmod +x dropShell.sh"