Release Jetpants 0.8.0

General changes:
* Better support for managing multiple versions of MySQL. Master promotion
  now refuses to promote a higher-version master if there are lower-version
  slaves present, for example. Jetpants has also now been tested extensively
  on Percona Server 5.5.
* Automatic management for enabling read_only on slaves. You can now enable
  read_only as a stock entry in your my.cnf (for all nodes, not just slaves)
  and Jetpants will properly disable it on the new master when performing a
  master promotion or shard split.
* When cloning a node, ib_lru_dump is copied too, if present. This file
  contains the buffer pool LRU list if your version of MySQL supports it;
  copying it allows newly-cloned nodes to warm up substantially faster, as
  well as potentially catch up on replication more quickly.
* Jetpants no longer attempts to manipulate my.cnf to do things like
  temporarily disabling binary logging during a bulk import. Instead, it now
  restarts MySQL with extra options supplied on the command-line, and
  afterwards restarts MySQL with no options on the command line. This is far
  less brittle when configuration management tools are in use.

Configuration changes:
* Reduced the default max_concurrency configuration value to 20. (was 40 in
  previous releases.)
* If a global Jetpants config (/etc/jetpants.yaml) and user-specific
  config (~/.jetpants.yaml) both exist, the user-specific one now selectively
  overrides the global via a "deep" merge of the YAML. For example, the user-
  specific config can add additional plugins without having to redeclare the
  original plugin list from the global config.
* Added a new configuration option, private_interface, specifying the name of
  the interface to use for the private LAN.

Command line toolkit changes:
* jetpants clone_slave now accepts input of "spare" (or multiples ie "spare,
  spare") to pull target machines from the spare queue.
* jetpants destroy_slave now works on targets that are offline or have broken
  replication. It also now calls revoke_all_access on targets as a safety
  mechanism (for example, to prevent app servers with old configuration info
  from being able to connect)
* jetpants summary now accepts pool names, in addition to node IPs

Bundled plugin changes:
* jetpants_collins can now optionally set state when setting status. To use
  this, call DB#collins_set(status: 'Foo', state: 'BAR').
* jetpants_collins now optionally allows you to override the Collins selector
  used for querying spare nodes, as well as the verification logic used to
  confirm that a spare is in a usable state.

Core class changes:
* Spare-node counting/claiming now passes another node for context. This can
  be used to build automation around having some pools with a different
  hardware spec, MySQL version, etc.
* The output of DB#data_set_size now includes the size of ibdata1.
* Improved DB#version_tuple to work on nodes with mysqld stopped, and added
  more version-related methods DB#normalized_version and DB#version_cmp.
* Pool#master_promotion! can now optionally exclude putting the old master
  into the pool as a slave, even if MySQL is still running. This can be
  useful when "evicting" an older-version master from a pool, as the last
  step in a MySQL upgrade.
* Deprecated DB#enable_binary_logging and DB#disable_binary_logging, and
  removed Host methods related to ini file manipulations.
* Added DB#poll_status_value to obtain the max or average of a global status
  field, and DB#max_threads_running which demonstrates its use.
* Added Host#pid_running? to check if a process is still running on a host.
* Fix bug in Topology#shard_for_id returning nondeterministic results during
  a shard split.
* More output in methods that manipulate replication or users/privileges.
* Add method DB#pause_replication_with to stop two slaves at the same
  coordinates.
* Add the ability to pass an after_connect hook to Sequel, and use it to
  disable unique_checks before import queries.
* Numerous other new methods added to the base DB, Host, and Pool classes.