Add a test for mapPropsOnChange

[wuct]

This PR shows an unexpected behavior of mapPropsOnChange.

Please see #119

[codecov-io]

Current coverage is 98.23%

Merging #132 into master will not affect coverage as of b19a3a4

@@            master    #132   diff @@
======================================
  Files           40      40       
  Stmts          283     283       
  Branches         0       0       
  Methods          0       0       
======================================
  Hit            278     278       
  Partial          0       0       
  Missed           5       5       

Review entire Coverage Diff as of b19a3a4

Powered by Codecov. Updated on successful CI builds.

[wuct]

I am not sure why the Travis CI build passed, but there is a test failed (as expected).

  ✖ mapPropsOnChange maps subset of owner props to child props   
  t.is(div.prop('c'), 'baz')
           |                
           "c"              

  1 test failed
  1. mapPropsOnChange maps subset of owner props to child props
  AssertionError: 'c' === 'baz'

[acdlite]

@wuct Yeah I'm aware of the false positives on Travis. It's due to the Ava workaround script we're using.