Merge develop (web3#1242)

* remove duplicate line (web3#1086) (web3#1098)

* Align text for unitMap (web3#1127)

* fixing compiler errors (web3#1174)

* Added web3j-scala to the list of Other Implementations (web3#1206)

* Extends HttpProvider with custom http headers (web3#1228)

* extend HttpProvider with custom http headers

* reset formatting

* reset formatting

* reset formatting

* fix null object

* fix null object

* Adds checksum isAddress() test cases (web3#1224)

* fixed tests

* build files

Author: frozeman

README.md

@@ -130,6 +130,7 @@ npm test
  - Python [Web3.py](https://github.com/pipermerriam/web3.py)
  - Haskell [hs-web3](https://github.com/airalab/hs-web3)
  - Java [web3j](https://github.com/web3j/web3j)
+ - Scala [web3j-scala](https://github.com/mslinn/web3j-scala)
 
 
 [npm-image]: https://badge.fury.io/js/web3.png