Strategy optimization

[pyoor]

This commit adds a number of improvements to the primary reduction strategy:

• Increment chunk_start by 1 instead of power of 2 when chunk_size <= 2
• Reduce from bottom up
• Add callback for performing actions at end of pass

Also included in this commit is a new reduction strategy which uses the postRoundCallBack for collapsing empty curly braces as an add-on to the primary reduction strategy.

[nth10sd]

Also please look at the linter test failures in Travis/AppVeyor.

[nth10sd]

We should also update the docs to reflect that Lithium will now reduce backwards.

[codecov-io]

Codecov Report

Merging #59 into master will increase coverage by 0.44%. The diff coverage is 95.57%.

@@            Coverage Diff             @@
##           master      #59      +/-   ##
==========================================
+ Coverage   84.61%   85.05%   +0.44%     
==========================================
  Files          13       13              
  Lines        1709     1767      +58     
==========================================
+ Hits         1446     1503      +57     
- Misses        263      264       +1

Impacted Files	Coverage Δ
tests/test_lithium.py	95.65% <100%> (+0.23%)	:arrow_up:
src/lithium/interestingness/utils.py	56.38% <20%> (ø)	:arrow_up:
src/lithium/reducer.py	81.49% <98.7%> (+0.5%)	:arrow_up:

---

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 ce510ba...af82da3. Read the comment docs.