Allow you to pass savon client configuration options

[drubin]

I fixed the specs as well.

Hope this is ok? I wanted to make it generic enough to allow you to pass through any configuration options directly to Savon.

Also updated the readme to include some defaults.

[wingrunr21]

There should not be a savon_globals option. You should be able to pass in arbitrary configuration parameters and we just consume what we care about. The rest should be delegated on to Savon itself:

MindBody.configure do |config|
  config.site_ids    = -99 # Consumed
  config.source_key  = 'abcd1234' # Consumed
  config.source_name = 'SuperFoo' #Consumed
  config.log_level   = :info # Passed to Savon
  config.encoding = 'UTF-8' # Passed to Savon
  ... #etc
end

This also allows log_level, open_timeout, read_timeout to once again be Savon's responsibility.

[drubin]

References #26

@wingrunr21 the internals might need some clean up but the API should remain consistent and allows us to only use the configs we care about everything else is passed through to Savon.