remove the following warnings

```
warning: "not expr1 in expr2" is deprecated. Instead use "expr1 not in expr2" if you require Elixir v1.5+, or "not(expr1 in expr2)" if you have to support earlier Elixir versions
```

lib/power_assert/assertion.ex

@@ -168,7 +168,7 @@ defmodule PowerAssert.Assertion do
     {ast, %{detector | in_fn: detector.in_fn + 1}}
   end
   @ignore_ops [:., :__aliases__, :|>, :==, :!=, :<, :>, :>=, :<=, :*, :||, :&&, :<>, :===, :!==, :and, :or, :=~, :%{}, :%, :->, :|, :{}]
-  defp pre_collect_position({func, _, args} = ast, detector) when not func in @ignore_ops and is_atom(func) and is_list(args) do
+  defp pre_collect_position({func, _, args} = ast, detector) when not(func in @ignore_ops) and is_atom(func) and is_list(args) do
     case Atom.to_string(func) do
       <<"sigil_", _name>> ->
         {ast, %{detector | in_fn: detector.in_fn + 1}}
@@ -281,7 +281,7 @@ defmodule PowerAssert.Assertion do
   # import List
   # [1, 2] |> first()
   #           ^
-  defp collect_position({func, _, args} = ast, %Detector{in_fn: in_fn} = detector) when not func in @ignore_ops and is_atom(func) and is_list(args) and in_fn > 0 do
+  defp collect_position({func, _, args} = ast, %Detector{in_fn: in_fn} = detector) when not(func in @ignore_ops) and is_atom(func) and is_list(args) and in_fn > 0 do
     case Atom.to_string(func) do
       # not supported sigils
       <<"sigil_", _name>> ->
@@ -290,7 +290,7 @@ defmodule PowerAssert.Assertion do
         {ast, detector}
     end
   end
-  defp collect_position({func, _, args} = ast, detector) when not func in @ignore_ops and is_atom(func) and is_list(args) do
+  defp collect_position({func, _, args} = ast, detector) when not(func in @ignore_ops) and is_atom(func) and is_list(args) do
     func_code = Macro.to_string(ast)
     matches = Regex.scan(~r/(?<!\.)#{Regex.escape(func_code)}/, detector.code, return: :index)
     positions = insert_pos_unless_exist(detector.positions, matches, func_code)
@@ -366,7 +366,7 @@ defmodule PowerAssert.Assertion do
   defp pre_catcher({func, _, [_, _]} = ast, injector) when func in @unsupported_func_arity2 do
     {ast, %{injector | in_fn: injector.in_fn + 1}}
   end
-  defp pre_catcher({func, _, args} = ast, injector) when not func in @ignore_ops and is_atom(func) and is_list(args) do
+  defp pre_catcher({func, _, args} = ast, injector) when not(func in @ignore_ops) and is_atom(func) and is_list(args) do
     case Atom.to_string(func) do
       <<"sigil_", _name>> ->
         {ast, %{injector | in_fn: injector.in_fn + 1}}
@@ -441,15 +441,15 @@ defmodule PowerAssert.Assertion do
       {ast, %{injector | in_fn: injector.in_fn - 1}}
     end
   end
-  defp catcher({func, _, args} = ast, %Injector{positions: [_h|_t], in_fn: in_fn} = injector) when not func in @ignore_ops and is_atom(func) and is_list(args) and in_fn > 0 do
+  defp catcher({func, _, args} = ast, %Injector{positions: [_h|_t], in_fn: in_fn} = injector) when not(func in @ignore_ops) and is_atom(func) and is_list(args) and in_fn > 0 do
     case Atom.to_string(func) do
       <<"sigil_", _name>> ->
         {ast, %{injector | in_fn: injector.in_fn - 1}}
       _ ->
         {ast, injector}
     end
   end
-  defp catcher({func, _, args} = ast, %Injector{positions: [[pos, _]|t]} = injector) when not func in @ignore_ops and is_atom(func) and is_list(args) do
+  defp catcher({func, _, args} = ast, %Injector{positions: [[pos, _]|t]} = injector) when not(func in @ignore_ops) and is_atom(func) and is_list(args) do
     {store_value_ast(ast, pos), %{injector | positions: t}}
   end
   defp catcher({variable, _, el} = ast, %Injector{in_fn: in_fn} = injector) when is_atom(variable) and is_atom(el) and in_fn > 0, do: {ast, injector}