added write_structure_tree<HTML_FORMAT> output.

most of the time we generate the html file with the extra binary in the
example dir anyway. this will increase the code size but in the end it
is a useful functionality to have.
Merge pull request #36 from mpetri/html_write_stucture_tree

added write_structure_tree<HTML_FORMAT> output.
Add in-memory tests to byte wavelet trees.
Removed unnecessary laod_from_file specialization.

Initialize memory with int_vector<8> instead and
use load_vector_from_file(...,...,1) to load
an byte file instead.
Added testing of in-memory construction.
Also execute wt-int-test.
Reduced test case size.
Merge pull request #37 from simongog/in-memory-tests

In memory tests
Test for bidirectional search
Fixed includes
Changed to TYPED_TEST
Do tests more often
Added ram_filebuf and adpated ram_fs.

TODO: xsputc is implemented but seems to be not called
by write.
Merge pull request #38 from simongog/search_bidirectional_test

Test for bidirectional search
Replaced emplace by insert.
Merge pull request #39 from simongog/ram_fstreambuf

Added ram_filebuf and adpated ram_fs.