Datasort, defrag, caching, documentation and CI

This pull request mostly described in 23b5487:

Most changes can be summarized as:
    * Replaced defrag with data-sort routine: it's responsible
        for defragmentation, index and data sorting.
    + Added binlog layer that can copy all data modification for
        specific base to binary log and then apply records to another one.
    + Added travis-ci integration (pun intended).
    + Added Doxyfile for Doxygen autogenerated documentation.
    - Removed unused routines like Atomic and ThreadSpinlock.
    - Removed caching of on-disk entries.
    * Renamed test_datasort to eblob_stress
    * Moved documentation to doc/

Datasort and Binlog functionality is described on reverbrain's wiki's blueprints:
http://doc.reverbrain.com/blueprints:eblob:data-sort
http://doc.reverbrain.com/blueprints:eblob:binlog