Prepare for 0.4.0 release

[addisonlynch]

• closes Dividends output formatting broken #110
• tests added / passed
• passes git diff upstream/master -u -- "*.py" | flake8 --diff
• added entry to docs/source/whatsnew/vLATEST.txt

[codecov]

Codecov Report

Merging #111 into master will decrease coverage by 3.85%.
The diff coverage is 70.58%.

@@            Coverage Diff             @@
##           master     #111      +/-   ##
==========================================
- Coverage   90.53%   86.68%   -3.86%     
==========================================
  Files          34       38       +4     
  Lines        2198     2366     +168     
==========================================
+ Hits         1990     2051      +61     
- Misses        208      315     +107

Impacted Files	Coverage Δ
iexfinance/base.py	80.51% <ø> (+1.29%)	⬆️
iexfinance/iexdata/base.py	97.45% <ø> (-0.04%)	⬇️
iexfinance/account/base.py	52.94% <ø> (ø)
setup.py	94.73% <ø> (ø)	⬆️
iexfinance/tests/test_apidata.py	63.63% <100%> (ø)
iexfinance/stocks/crypto.py	100% <100%> (ø)	⬆️
iexfinance/stocks/__init__.py	95.34% <100%> (ø)	⬆️
iexfinance/tests/test_account.py	43.33% <100%> (ø)	⬆️
iexfinance/stocks/collections.py	100% <100%> (ø)	⬆️
iexfinance/altdata/base.py	36.36% <36.36%> (ø)
... and 17 more

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