copy files from wp-includes/export verbatim
copy wp-includes/iterators.php to export/iterators.php
load Oxymel via Composer
load export classes via Composer
first pass at loading and using the export API

* replace --file_item_count with --max_file_size
* --verbose is ignored, for now
add _wp_export_build_IN_condition() helper
log each exported file path

had to copy over the whole WP_Export_Split_Files_Writer class.
remove --verbose parameter

The idea is to be reasonably verbose by default and completely silent
when --quiet is passed.
Restore af65fe41c8d3b9df3c1fb1461fddf92ac165fde5, which I accidentally overwrote :(
set Oxymel to version 0.1.0
merge master into export-api branch
Merge branch 'master' into export-api
replace VerboseExportWriter class with 'wp_export_new_file' hook
behat: fix import by making the export message match the expected format again
Merge branch 'master' into export-api
behat: check STDERR when running `wp export`
implement 'wp post generate --post_content=<content>'
Introduce a helper method for launching a new WP-CLI process using the same context as the current process.
Now that we have a method to launch new WP-CLI processes, use it to flush rewrite rules after setting the structure.

Fixes #814
These arguments should be optional