Add note regarding underscore prefix on template variable names.

NEWS.md

@@ -22,3 +22,6 @@ Standards](http://www.gnu.org/prep/standards/html_node/NEWS-File.html#NEWS-File)
 
 * Renamed compile options for `translation_fun` and `locales` to align
   with the render options counter parts.
+
+* Support `_` prefix on template variables to avoid unused variable
+  warnings, Erlang style (#164).

README.markdown

@@ -504,6 +504,9 @@ Differences from standard Django Template Language
 * For an up-to-date list, see all
   [issues](https://github.com/erlydtl/erlydtl/issues) marked
   `dtl_compat`.
+* Erlang specifics: Template variables may be prefixed with underscore
+  (`_`) to avoid "unused variable" warnings (see
+  [#164](https://github.com/erlydtl/erlydtl/issues/164)).
 
 
 Tests