Fix Travis

[kremalicious]

Trying to fix Travis

• bump Node.js version, build current and last version
• bump Tendermint version as done in Problem: the driver is using an old tendermint version bigchaindb-driver#412
• ESlint fixes: use locally installed version, examples fixes
• delete yarn.lock (cause it's ignored by .gitignore so shouldn't be there)

Also closes #168

[codecov-io]

Codecov Report

Merging #172 into master will increase coverage by 3.89%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master     #172      +/-   ##
==========================================
+ Coverage   80.54%   84.43%   +3.89%     
==========================================
  Files          11       11              
  Lines         257      257              
==========================================
+ Hits          207      217      +10     
+ Misses         50       40      -10

Impacted Files	Coverage Δ
src/transaction.js	97.5% <0%> (+6.25%)	⬆️
src/utils/ccJsonify.js	80.76% <0%> (+19.23%)	⬆️

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[kremalicious]

Travis is green again