Add :atomize_keys config option that allows disabling to_atom on user input

It's not a good idea to turn arbitrary HTML classes into atoms:
https://engineering.klarna.com/monitoring-erlang-atoms-c1d6a741328e

lib/implied.ex

@@ -6,7 +6,8 @@ defmodule Microformats2.Items.ImpliedProperties do
   end
 
   defp implied_url_property(entry, root, doc_url, doc) do
-    if entry[:properties][:url] == nil do
+    url_key = if Application.get_env(:microformats2, :atomize_keys, true), do: :url, else: "url"
+    if entry[:properties][url_key] == nil do
       val = implied_url_attrval(root)
 
       url =
@@ -20,7 +21,7 @@ defmodule Microformats2.Items.ImpliedProperties do
       if Microformats2.blank?(url) do
         entry
       else
-        Map.put(entry, :properties, Map.put(entry[:properties], :url, [Microformats2.abs_uri(url, doc_url, doc)]))
+        Map.put(entry, :properties, Map.put(entry[:properties], url_key, [Microformats2.abs_uri(url, doc_url, doc)]))
       end
     else
       entry
@@ -28,7 +29,8 @@ defmodule Microformats2.Items.ImpliedProperties do
   end
 
   defp implied_photo_property(entry, root) do
-    if entry[:properties][:photo] == nil do
+    photo_key = if Application.get_env(:microformats2, :atomize_keys, true), do: :photo, else: "photo"
+    if entry[:properties][photo_key] == nil do
       val = implied_photo_attrval(root)
 
       url =
@@ -42,7 +44,7 @@ defmodule Microformats2.Items.ImpliedProperties do
       if Microformats2.blank?(url) do
         entry
       else
-        Map.put(entry, :properties, Map.put(entry[:properties], :photo, [url]))
+        Map.put(entry, :properties, Map.put(entry[:properties], photo_key, [url]))
       end
     else
       entry
@@ -50,7 +52,8 @@ defmodule Microformats2.Items.ImpliedProperties do
   end
 
   defp implied_name_property(entry, root = {elem, _, _}) do
-    if entry[:properties][:name] == nil do
+    name_key = if Application.get_env(:microformats2, :atomize_keys, true), do: :name, else: "name"
+    if entry[:properties][name_key] == nil do
       nam =
         cond do
           elem == "img" or elem == "area" ->
@@ -70,7 +73,7 @@ defmodule Microformats2.Items.ImpliedProperties do
         end
         |> Microformats2.stripped_or_nil()
 
-      Map.put(entry, :properties, Map.put(entry[:properties], :name, [nam]))
+      Map.put(entry, :properties, Map.put(entry[:properties], name_key, [nam]))
     else
       entry
     end

lib/items.ex

@@ -132,14 +132,16 @@ defmodule Microformats2.Items do
   defp parse_prop(_, _, _, _), do: nil
 
   defp get_value(class, p) do
+    name_key = if Application.get_env(:microformats2, :atomize_keys, true), do: :name, else: "name"
+    url_key = if Application.get_env(:microformats2, :atomize_keys, true), do: :url, else: "url"
     cond do
-      Microformats2.is_a?(class, "p") and p[:properties][:name] != nil ->
-        List.first(p[:properties][:name])
+      Microformats2.is_a?(class, "p") and p[:properties][name_key] != nil ->
+        List.first(p[:properties][name_key])
 
-      Microformats2.is_a?(class, "u") and p[:properties][:url] != nil ->
-        List.first(p[:properties][:url])
+      Microformats2.is_a?(class, "u") and p[:properties][url_key] != nil ->
+        List.first(p[:properties][url_key])
 
-      # and p[:properties][:url] != nil ->
+      # and p[:properties][url_key] != nil ->
       Microformats2.is_a?(class, "e") ->
         # TODO handle
         nil
@@ -160,7 +162,8 @@ defmodule Microformats2.Items do
             parse_prop(class, child, doc, url)
           end
 
-        key = strip_prefix(class) |> to_key |> String.to_atom()
+        key = strip_prefix(class) |> to_key
+        key = if Application.get_env(:microformats2, :atomize_keys, true), do: String.to_atom(key), else: key
         val = if acc[key] != nil, do: acc[key], else: []
         Map.put(acc, key, val ++ [prop])
       end)