Changed event.XPath API and propagate changes to engine.Event structu…

…res + improved overall coverage

Changes:

 - more Load functions
 - refactored engine.Load in engine.LoadFile
 - made engine.AddRule private

Changed LoadContainer function to use bufio + Test case + removed Tra…

…ces feature leftovers

Added allowed characters in container names

Changed Rule.Compile API + added code coverage

Version bump of golang-utils fixing datastructs.Set JSON marshaling o…

…rder

Fixed bounded score formula in case we divide by 0

Solved Golang v2 package compatibility issue

Fixed Version JSON marshaling

Fixed issues:

    - #19 Document new rule format
    - #18 Create a bounded score in reducer
    - #17 change rule format
    - #16 Use TOML for regex templates
    - #15 Implement default actions
    - #14 Define an Event interface
    - #13 Make fails when shell doesn't have $GOPATH

Changes:
    - package refactoring (rules package moved inside engine package)
    - code refactoring:
        - No more engine.Match only engine.MatchOrFilter
        - Detection structure to hold detection information
    - project version bump