Refactored test setup code

Removed the copy/paste code, moved it into a reusable function that can
be called from the `local_setup` function as needed. Also simplified the
handling of the $HOME variable since @rico-chet provided a better way of
doing this.

test/plugins/ruby.plugin.bats

@@ -6,21 +6,7 @@ load ../../lib/composure
 load ../../plugins/available/ruby.plugin
 
 function local_setup {
-  mkdir -p "$BASH_IT"
-  lib_directory="$(cd "$(dirname "$0")" && pwd)"
-  # Use rsync to copy Bash-it to the temp folder
-  # rsync is faster than cp, since we can exclude the large ".git" folder
-  rsync -qavrKL -d --delete-excluded --exclude=.git --exclude=enabled $lib_directory/../../../.. "$BASH_IT"
-
-  rm -rf "$BASH_IT"/enabled
-  rm -rf "$BASH_IT"/aliases/enabled
-  rm -rf "$BASH_IT"/completion/enabled
-  rm -rf "$BASH_IT"/plugins/enabled
-
-  mkdir -p "$BASH_IT"/enabled
-  mkdir -p "$BASH_IT"/aliases/enabled
-  mkdir -p "$BASH_IT"/completion/enabled
-  mkdir -p "$BASH_IT"/plugins/enabled
+  setup_test_fixture
 
   export OLD_PATH="$PATH"
   export PATH="/usr/bin:/bin:/usr/sbin"