Change unset to take an array as default, added tests when pass parameters as array or object
Alias takes a callback.
Verbose is config option.
Fix test.
Fix other test.
Merge branch 'master' of https://github.com/lukapril/mixpanel-node
fixed issues with unset
Merge branch 'alias-takes-callback' of https://github.com/spanishdict/mixpanel-node
Merge branch 'verbose-config-option' of https://github.com/spanishdict/mixpanel-node
Bumped to version 0.0.18

* added callback to alias (thanks to sandinmyjoints)
* added verbose config option (thanks to sandinmyjoints)
* added unset method (thanks to lukapril)