Mkdocs-macros-plugin

* Improved user guide, with introduction of two new pages:
"Controlling macro rendering" and "Post production".

* Fixed: (158) In modules, `on_pre_page_macros()`, the `env.markdown`
attribute is now available to create a header or footer.

* Changed: In `on_post_page_macros()` use `env.markdown` instead of
`env.raw_markdown`, for the same purpose.

* Added: (162) Allow opt-in of page rendering, by using parameter
`render_macros: true` in yaml header of the page
(requires `render_by_default:false` in the macro parameters,
in the config file).

* Fixed: `macro_info()` now generates a header of category 2,
so as to be used with other material in the same page,
and not confuse the macro generators.

* Changed: `ignore_macros: true` in page header is deprecated.
Use `render_macros: false` instead.

* Fixed: issues 155 (documentation type), 143 (`git.tab`),
135 (indicate page where rendering failed).

* Bump version to 1.1.0 to acknowledge that API is stable.

* Added: (133) `on_error_fail` in config file to make build/serve process
fail in case of macro error, with return code 100.

* Added: (130) Documentation on the tree structure of a typical
macro directory (package)

* Fixed: (118) `{{ git.date }}` is now committer date (no longer author date).
* Added: new git info elements (author email, committer, committer email);
documentation was updated
* Added: by default, unknown variables in a markdown page (`{{ foo }}`)
are no longer replaced by blanks but displayed as is (DebugUndefined) (117);
for better compatibility with other plugins or error detection
* Added: `on_undefined` parameter in plugin definition to alter behavior
with unknown jinja2 variables: 'keep' (default), 'silent', 'strict', 'lax';
documentation was updated

* Fixed: Broken build of 0.6.2

* Added: `env.markdown` is now modifiable, for use in `on_post_page_macros()`

* Added: auto-install of pluglets (in `module` parameter in config file)