fix: Reduce memory leaks (#148)

It is not 100% clear that we've gotten ALL the memory leaks, but it
seems much much much better and doesn't look like it's going to die
immediately or as often anymore :)

lua/tests/manual/newline_tables.lua

@@ -1,15 +1,23 @@
-require('plenary.reload').reload_module('telescope')
+-- require('plenary.reload').reload_module('telescope')
 
 local finders = require('telescope.finders')
 local pickers = require('telescope.pickers')
 local sorters = require('telescope.sorters')
+local previewers = require('telescope.previewers')
 
-local my_list = {'a', 'b', 'c'}
+local my_list = {
+  'lua/telescope/WIP.lua',
+  'lua/telescope/actions.lua',
+  'lua/telescope/builtin.lua',
+}
 
-pickers.new({
+local opts = {}
+
+pickers.new(opts, {
   prompt    = 'Telescope Builtin',
   finder    = finders.new_table {
     results = my_list,
   },
   sorter    = sorters.get_generic_fuzzy_sorter(),
+  previewer = previewers.cat.new(opts),
 }):find()