add bookshelf stress tests

The bookshelf bench stress tests are intended to put bookshelf under
sufficient load so that we can attch to the vm and use debugging
tools and techniques to monitor the performance and health of the
bookshelf system.
Revert "Convert file IO to raw mode"

This reverts commit 12f2c91283c7387365dc54b7e4b16ec1236e06e5.

Reverting this commit fixes the process consumption behavior that we've
been seeing with the latest builds of bookshelf under heavy load. The
stress tests in the `stest` directory can be used to confirm the
behavior.
Merge branch 'sd/process-leak-bench'
bookshelf 1.1.2

Updated deps:

  eper
    2014-01-20 aa2b872 v0.79
    2014-01-20 fad22c4 work around edoc choking on spec x()->A..B.
    2014-01-16 69364c7 v0.78
    2014-01-16 8477496 fix watchdog:add_send_subscriber(integer(),,,)
    2013-12-19 f12c231 add redbug_msc unit tests
    2013-12-18 7fc126f eunit-ify redbug_msc unit tests
    2013-12-18 5cf62f1 v0.77
    2013-12-18 171efd5 .gitignore priv/bin/eper
    2013-12-18 bfd00bd v0.76
    2013-12-18 9e598dd put eper script in priv/bin
    2013-12-18 ebc436b fix redbug print-to-text-file
    2013-12-06 7b57394 renamed getopt to solve name clash

  rebar_lock_deps_plugin
    2014-01-17 911481e Merge pull request #10 from seth/sf/rebar.config.script
    2014-01-16 7d24910 Respect rebar.config.script by using  rebar_config:consult_file/1
    2013-12-24 c190c07 Merge branch 'keep-dep-order'
    2013-12-20 71cbcc7 Respect order of rebar.config files when generating lock file
    2013-12-20 f99e917 Fix list_deps_versions to handle dep tuples with URLs