Added rdiv function for tensors, completed mean functions, started ma…

[felix91gr]

…x functions and added one (of four required) tests for max

• At rdivide: added Tensor division by Int and Double
• At mean: impĺemented Tensor mean functions. They need testing
• At _max: implemented trivial max functions for List, Vector, Matrix and Tensor.
• At max_test: implemented test for List
• At mean_test: divided basicTest into more atomic ones. Added List test.

[codecov-io]

Codecov Report

Merging #23 into master will decrease coverage by 0.32%. The diff coverage is 67.39%.

@@            Coverage Diff             @@
##           master      #23      +/-   ##
==========================================
- Coverage   88.36%   88.03%   -0.33%     
==========================================
  Files         211      212       +1     
  Lines        5379     5424      +45     
==========================================
+ Hits         4753     4775      +22     
- Misses        626      649      +23

Impacted Files	Coverage Δ
Sources/rdivide.swift	25% <ø> (-25%)	:arrow_down:
Sources/mean.swift	62.5% <0%> (-37.5%)	:arrow_down:
Tests/NiftyTests/mean_test.swift	100% <100%> (ø)	:arrow_up:
Tests/NiftyTests/max_test.swift	100% <100%> (ø)	:arrow_up:
Sources/_max.swift	40% <40%> (ø)

---

Continue to review full report at Codecov.

Legend - Click here to learn more Δ = absolute <relative> (impact), ø = not affected, ? = missing data Powered by Codecov. Last update 7bb5ba5...57f0b38. Read the comment docs.