Added support for new MongoDB operators since 2.6 (fix #10)

[kell18]

Hi! It's me again!
As promised - simple PR with new operators.
Fixes #10

[codecov-io]

Codecov Report

Merging #12 into master will increase coverage by 0.05%.
The diff coverage is 100%.

@@            Coverage Diff             @@
##           master      #12      +/-   ##
==========================================
+ Coverage    95.8%   95.86%   +0.05%     
==========================================
  Files          13       13              
  Lines         143      145       +2     
  Branches        5        5              
==========================================
+ Hits          137      139       +2     
  Misses          6        6

Impacted Files	Coverage Δ
...b/limansky/mongoquery/core/bsonparser/Parser.scala	100% <100%> (ø)	⬆️

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[limansky]

LGTM