Update rebar

Update to newer version of rebar so that a commit hash can be
used in deps list.
Fix all deps to a specific version

If you don't fix deps to a specific version then you run the
chance of an API change breaking the drivers.
add needed cassandra config options
Merge pull request #36 from basho/rz-fix-deps

fix dependencies to specific versions/tags
Add 'sequential_int_state_dir' config item, resume on crash/restart
Add 'sequential_int_state_dir' to examples
adding a cassandra driver using cql
fixing typo
Allow basho_bench to pre-compute and pre-load Riak vnode data dirs.

Currently this only works with the eleveldb driver.  For maximum
utility, it should be extended to work with bitcask and other
Riak backends.
Add comments to examples/shortcut.config
Add support for Bitcask

Test method:

* Use the `examples/shortcut.config` file as shown to pre-populate 50K keys.
  Change the `code_paths` and `shortcut_data_dir` to reflect your
  environment.
* Run `./basho_bench ./examples/shortcut.config`
* Over on a Riak console, use:
  * {ok, C} = riak:local_client().
  * [ok] = lists:usort([catch element(1, C:get(<<"b1">>, <<X:32/native>>)) || X <- lists:seq(0,49999)]).
fixing quotation typo
Add support for experimental hanoidb storage manager
Refactor preflist calculation, clean up debugging cruft
Deprecate the int_to_bin key generator, add 2 others to replace it
adding support for insert, put, get, delete methods as well as some code to keep track of existing and deleted keys
fixing updates and adding support for normal valgen
removing file manipulation dependencies from opeartion functions
Add Travis CI hook and status image.
fixing comments