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)]).
Add support for experimental hanoidb storage manager
Refactor preflist calculation, clean up debugging cruft
verify seq_int resume value is not out of bounds
Updated http_raw driver to allow appending custom headers in the .config file, which is useful for things like HTTP Auth.
add delete support for basho_bench_driver_http_raw
Merge pull request #71 from basho/sbv-add-raw-http-delete

add delete support for basho_bench_driver_http_raw
Fix incorrect error case clauses
Merge pull request #73 from basho/eas-fix-err-case-clauses

Fix incorrect error case clauses
Remove non-source file from src dir
Add uniform_int start/#keys generator

I needed this when testing a 2i problem that involved only big integers.
Merge pull request #74 from basho/eas-add-uniform-int-range

Add uniform_int start/#keys generator
Add additional configuration items to basho_bench_driver_riakc_pb.erl

* pb_connect_options, list(two_tuple()), list of valid Protocol Buffers
  client connection options.
  Default = [{auto_reconnect, true}]

NOTE: The new default value creates a change in behavior of the
      PB client: the default is {auto_reconnect, false}.  Users
      of the PB client that wish the old & brittle behavior of
      crashing on server-side errors, timeouts, etc. must provide
      explicit configuration now to disable auto_reconnect behavior.

* pb_timeout_general, integer(), overall single Protocol Buffer
  operation timeout value.
  Default = 62000
  Units = milliseconds

* pb_timeout_read, integer(), overall single Protocol Buffer
  read operation timeout value.
  Default = value of pb_timeout_general
  Units = milliseconds

* pb_timeout_write, integer(), overall single Protocol Buffer
  write operation timeout value.
  Default = value of pb_timeout_general
  Units = milliseconds

* pb_timeout_listkeys, integer(), overall single Protocol Buffer
  listkeys operation timeout value.
  Default = value of pb_timeout_general
  Units = milliseconds

* pb_timeout_mapreduce, integer(), overall single Protocol Buffer
  mapreduce operation timeout value.
  Default = value of pb_timeout_general
  Units = milliseconds
Fix partitioned seq int gen leaving some keys out

Fixes #75
For example, with 12 workers and 100 keys, it leaves the 4 last keys out
(100 rem 12).  This makes those keys (at most # of workers) be given to
the last worker.
Merge pull request #76 from basho/eas-fix-remainder-partitioned-seq-int

Fix partitioned seq int gen leaving some keys out
Merge of branch  slf-bulk-insert-shortcut2
Merge pull request #68 from joecaswell/jhc-resumecheck

verify seq_int resume value is not out of bounds
Merge pull request #69 from nathanaschbacher/master

Updated http_raw driver to allow appending custom headers.