Rename dexa to just exa

Vagrantfile

@@ -55,10 +55,9 @@ Vagrant.configure(2) do |config|
     # Create "dexa" and "rexa" scripts that run the debug and release
     # compiled versions of exa.
     config.vm.provision :shell, privileged: true, inline: <<-EOF
-        echo -e "#!/bin/sh\necho \"Use 'dexa' for debug exa, or 'rexa' for release exa\"" > /usr/bin/exa
-        echo -e "#!/bin/sh\n/home/#{developer}/target/debug/exa \\$*" > /usr/bin/dexa
+        echo -e "#!/bin/sh\n/home/#{developer}/target/debug/exa \\$*" > /usr/bin/exa
         echo -e "#!/bin/sh\n/home/#{developer}/target/release/exa \\$*" > /usr/bin/rexa
-        chmod +x /usr/bin/{exa,dexa,rexa}
+        chmod +x /usr/bin/{exa,rexa}
     EOF