Add new nextUntil function, rename previous nextUntil to nextAll

prevUntil and nextUntil as written did not perform what I expected, returning a value akin to jQuery's prevAll and nextAll. This PR renames existing functions prevUntil and nextUntil to prevAll and nextAll, as well as adds more jQuery-like prevUntil and nextUntil functions instead. @ericmuyser provided me with a _until function he wrote.

Status: **Opened for review**
 
Reviewers: @hora @scalvert 
  
## Changes
- Renamed the helper function _until to _all
- Renamed prevUntil and nextUntil to prevAll and nextAll
- Added new _until helper function
- Added new prevUntil and nextUntil functions
- Added traversal tests
  
## How to test-drive this PR
- Install this branch into a project and compare behavior to a jQuery instance of nextAll and nextUntil
  
## Research resources
- http://api.jquery.com/nextall/
- http://api.jquery.com/nextuntil/