Write translated Markdown documentation pages in temporal directory

[mondeja]

Fixes #17

This is done, the problem is that PO files inside docs/ folder are written during the build, even if are written on post_build event. The possible solutions are:

• [x] Store PO translations in other folder outside of docs/. It seems very convenient to store them there, but currently Mkdocs does not offer a way to write to docs/ without entering in a infinite reload loop when serving files. Just using locale_dir and documeting it.
• [ ] Wait for https://github.com/mkdocs/mkdocs/pull/2777. This would allow to unwatch PO files. The problem here is that when PO file changes, it would not be reloaded, but this inconvenient doesn't seem very important anyways.

Breaking changes

• Default dest_filename_template has been changed from {{language}}/{{page.file.dest_path}} to {{language}}/{{file.dest_path}}.

[coveralls]

Pull Request Test Coverage Report for Build 1898981712

• 139 of 150 (92.67%) changed or added relevant lines in 7 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage decreased (-0.5%) to 96.398%

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Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
mkdocs_mdpo_plugin/plugin.py	70	74	94.59%
mkdocs_mdpo_plugin/config.py	12	19	63.16%
<!--	Total:	139	150	92.67%	-->

Totals
Change from base Build 999587926:	-0.5%
Covered Lines:	455
Relevant Lines:	472

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💛 - Coveralls