Generate gettext infrastructure
-------------------------------

Erlydtl allows templates to use i18n features based on gettext. Standard po
files can be used to generate i18ized templates. A template parser/po generator
is also provided.

Translation done by `{%trans%}`, `{%blocktrans%}` tags and by wrapping variables
in `_(...)` construction.

Translation may be applied in compile time (translated strings are embedded in
compiled template code) or in runtime (template will query gettext server during
template rendering). 1'st is faster in terms of template rendering time, 2'nd is
more flexible (you may update locales without any template recompilation).

In order to apply compile-time translation, you must pass `blocktrans_fun` plus
`blocktrans_locales` (this will translate `{%blocktrans%}`) and/or `locale` (this
translates `{%trans%}` and `_("string literal")` values) to `erlydtl:compile/3`.
Next, you should pass `locale` option to `my_compiled_template:render/2`.

If you prefer runtime translation, just don't pass `blocktrans_fun` and/or `locale`
compilation options and add `translation_fun` option to `my_compiled_template:render/2`.

    1.  In order to enable i18n you first, you'll need gettext library to be
        available on your lib_path. 

        Library can be downloaded from http://github.com/etnt/gettext

    2.  Then you'll need to add a parse target on your makefile (or the script
        used to trigger template reparsing) trans:

        erl -pa ./ebin ./deps/*/ebin -noshell -s reloader -run i18n_manager \
                               generate_pos "en,es" "./views/*/*.html,./views/*.html"
        rm -rf $(GETTEXT_DIR)/lang/default-old
        mv $(GETTEXT_DIR)/lang/default $(GETTEXT_DIR)/lang/default-old
        cp -rf $(GETTEXT_DIR)/lang/$(GETTEXT_TMP_NAME) $(GETTEXT_DIR)/lang/default
        rm -rf $(GETTEXT_DIR)/lang/$(GETTEXT_TMP_NAME)/*

        Mind that GETTEXT_DIR and GETTEXT_TMP_NAME must be bound to existing
        directories. Args passed to i18n_manager:generate_pos are locales that
        will be supported (generating dir structure and po files) and
        directories where generator will search for template files including
        trans tags.

    3.  If you wish to translate templates at compile-time, gettext server must be
        running before template parsing and it must be
        populated with the content of the po files. Consider adding this
        snipplet to the code before template parsing

	gettext_server:start(),
        LoadPo = 
            fun(Lang)->
                {_, Bin} = file:read_file("./lang/default/"++ Lang ++"/gettext.po"),
                gettext:store_pofile(Lang, Bin)
            end,
        lists:map(LoadPo, ["es","en"]).

        Here locales are the codes are provided to gettext. Those codes must be
        a subset of the locales provided to po generation process.

    4.  Update strings. Edit po files on $(GETTEXT_DIR)/lang/default/$(LOCALE)/gettext.po 
        translating msgstr to the translated version of their corresponding msgstr.

    5.  Generate localized templates providing `blocktrans_fun` and
        `blocktrans_locales` compile options or use runtime
        translation via `translation_fun` rendering option.
