work in progress: c++ port

This is because we want the text of the page in "raw order layout" (`pdftotext -raw`) which is not exposed for the C/Glib-API.

Remaining problem:
* we also want to use the text attribute list from the glib API (`poppler_page_get_text_attributes`) to build our semi-structured output array. This, however, isn't exposed in the C++ API... :trollface:

Using both bindings seems stupid, so I'll just copy the implementation of `poppler_page_get_text_attributes`, I think.

TODO
* [ ] update autoconfig
* [ ] add vagrant run on travis, fix leaks