Added a rule to R.cond warning if the last condition is not a R.T.

[mikepombal]

This PR adds the cond-default rule.

It suggests to have R.T as the last condition so it acts as the default value.

[codecov-io]

Codecov Report

Merging #27 into master will not change coverage.
The diff coverage is 100%.

@@          Coverage Diff          @@
##           master    #27   +/-   ##
=====================================
  Coverage     100%   100%           
=====================================
  Files          27     28    +1     
  Lines         249    258    +9     
=====================================
+ Hits          249    258    +9

Impacted Files	Coverage Δ
rules/cond-default.js	100% <100%> (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 2e3d75d...5f85308. Read the comment docs.