Add map and merge operators (WIP)

[jacksoncheek]

WIP - No tests added yet

Summary

• Add map operator (http://reactivex.io/documentation/operators/map.html)
• Add merge operator (http://reactivex.io/documentation/operators/merge.html)

[codecov[bot]]

Codecov Report

Merging #45 into master will decrease coverage by 10.3%. The diff coverage is 0%.

@@             Coverage Diff             @@
##           master      #45       +/-   ##
===========================================
- Coverage   87.15%   76.84%   -10.31%     
===========================================
  Files          17       17               
  Lines         179      203       +24     
  Branches       14       14               
===========================================
  Hits          156      156               
- Misses         18       42       +24     
  Partials        5        5

Impacted Files	Coverage Δ
...tlin/src/main/java/com/compass/snail/Observable.kt	69.09% <0%> (-19.29%)	:arrow_down:

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