v0.9.0-rc1

@samlecuyer @davglass @JerrySievert @adamstallard 

Probably the most amount of forward progress on vows in three years. 

1. Adds "Serial Vows" `Array` syntax. #162 
2. Allows for vows for events that execute multiple times #193
3. Allow for pending vows by adding `//` to the beginning of an Object key #211 
4. Expect a vow to be called `n` times #212 
5. `beforeSuite` and `afterSuite` #222 
6. `json-file` reporter #259 
7. Allow for multiple exports in required test files #284
8. Display a summary on process exit #252