0.9.0 release.

* **Breaking change**: Fixed typo in UnixBench benchmark name: now `UnixBench_benchmark` (GoogleCloudPlatformGH-50).
* **Breaking change**: removed `--json_output` flag. JSON samples are always
  written (GoogleCloudPlatformGH-41).
* **Breaking change**: `object_storage_service` requires a `.boto` file
  configured for AWS and GCS to function.
* **Breaking change:** updated benchmark names to be more consistent (GoogleCloudPlatformGH-72).
  Specific changes:

    + `cassandra` → `cassandra_stress`
    + `copy_benchmark` → `copy_throughput`
    + `fio_benchmark` → `fio`
    + `hadoop_benchmark` → `hadoop_terasort`
    + `mesh_benchmark` → `mesh_network`
    + `netperf_simple` → `netperf`
    + `object_storage_benchmark` → `object_storage_service`
    + `synthetic_storage_workloads_benchmark` → `block_storage_workload`
    + `sysbench_oltp_benchmark` → `sysbench_oltp`
    + `UnixBench_benchmark` → `unixbench`

* Added support for C4 instance types on EC2 (GoogleCloudPlatformGH-63).
* Added support for specifying `--product_name` on the command line (GoogleCloudPlatformGH-55).
* Added side-by-side comparison tool (GoogleCloudPlatformGH-39, GoogleCloudPlatformGH-61, GoogleCloudPlatformGH-62).
* Factored out package management to support RHEL, CentOS (GoogleCloudPlatformGH-54).
* Improved accuracy of cluster boot time (GoogleCloudPlatformGH-69, GoogleCloudPlatformGH-73).
* Introduced a class to represent performance samples (GoogleCloudPlatformGH-71)
* Updated Hadoop benchmark to calculate per-core terasort throughput (GoogleCloudPlatformGH-75).
* Added a results parser for bonnie++ benchmark (GoogleCloudPlatformGH-70).
* Added a results parser for fio benchmark (GoogleCloudPlatformGH-32).
* Added prerequisite checking to benchmarks (GoogleCloudPlatformGH-49).
* Switch to Apache distribution of Cassandra (GoogleCloudPlatformGH-92).
* Improved default behavior for machine types with no local storage (GoogleCloudPlatformGH-88).
* Updated `object_storage_service` benchmark to test both command line tool
  performance and direct API calls (GoogleCloudPlatformGH-59, GoogleCloudPlatformGH-90).
* Added benchmark sets: predefined collections of benchmarks to run (GoogleCloudPlatformGH-80).
* Modified HPCC benchmark to use 80% of available memory rather than 80% of
  total. Prevents crashes on low-memory systems (GoogleCloudPlatformGH-81).
* Updated the default Azure image (GoogleCloudPlatformGH-84).
* Improved the Cassandra stress benchmark to incorporate a user-specified
  number of rows, with defaults that run on all cloud platforms with default
  quotas (GoogleCloudPlatformGH-31).
* Improved the Cassandra stress benchmark to incorporate a user-specified
  number of cassandra-stress threads on client node, with defaults of 50
  (originally default was 300 which caused the benchmark to crash on small
  instance types). As a result, on large instance types, the throughput
  reported by cassandra-stress tool is lower than previous version (GoogleCloudPlatformGH-31).

Version 0.8.0

* Documentation cleanup (GoogleCloudPlatformGH-19, GoogleCloudPlatformGH-34).
* Fix incorrect assignment of `ip_type` metadata in `netperf_simple` benchmark (GoogleCloudPlatformGH-26).
* Added `--gcloud_scopes` flag, to support providing permissions to created instances on GCP.
* Changed GCP default image from `debian-7-backports` to `ubuntu-14-04`. All cloud providers now run Ubuntu 14.04 by default (GoogleCloudPlatformGH-43).
* Added results parser for MongoDB (GoogleCloudPlatformGH-36) and UnixBench++ (GoogleCloudPlatformGH-45).
* Improved unit test coverage (GoogleCloudPlatformGH-21).

Release v0.7.1

Changes:

* GCE VM SSH keys are now provided via a temporary file rather than the command
  line, which fixes a compatibility issue between versions of `gcloud` (GoogleCloudPlatformGH-19).

Release v0.7.0

* New benchmark: `aerospike` (GoogleCloudPlatformGH-13).
* `iperf`: Run benchmark in both directions (VM A -> VM B and B -> A) (GoogleCloudPlatformGH-7).
* `hadoop_benchmark`: Bump Hadoop to version 2.5.2 (GoogleCloudPlatformGH-5).
* `synthetic_storage_workloads_benchmark`: Fix IO sizes passed to `fio`.
* Add a verbose log to `/tmp/perfkitbenchmarker/run_<run_uri>/perfkitbenchmarker.log`
  (exact file name announced to stderr at start of run) (GoogleCloudPlatformGH-3).
* Merge `perfkitbenchmarker_lib` into `vm_util` (GoogleCloudPlatformGH-9)
* Refactor result publishing and metadata collection (GoogleCloudPlatformGH-10).
* Add a Google Cloud Storage publisher (GoogleCloudPlatformGH-14)
* Change the default Azure machine type to "Small".
* Added unit tests.
* Style fixes.

PerfKitBenchmarker release v0.6