Add RLP encoding library

[bakaoh]

Fix #170

The contract expose functions:

• encodeBytes(bytes memory self) internal pure returns (bytes)
• encodeAddress(address self) internal pure returns (bytes)
• encodeUint(uint self) internal pure returns (bytes)
• encodeInt(int self) internal pure returns (bytes)
• encodeBool(bool self) internal pure returns (bytes)
• encodeList(bytes[] memory self) internal pure returns (bytes)

[smartcontracts]

Hey @bakaoh, thanks for the PR. Could you update this contract so it passes the Travis build?

[bakaoh]

@kfichter --- it's look like the Travis build is fail in develop branch, i guess it's nothing to do with the contract. Should i change the base to master?

Edit: i changed the base to master

[bakaoh]

@kfichter --- i've updated

[smartcontracts]

Thank you! Merging :-)

[smartcontracts]

Hey @bakaoh would you be OK with making a standalone repository that contains this code? Would prefer you do it so you get credit :-)

[smartcontracts]

@bakaoh I went ahead and started the repository here, credited you in the contract and in the README. More than happy to transfer ownership of the repo!

[bakaoh]

Thanks @kfichter . I'm a bit busy lately so i can not maintain it now, please don't worry about ownership ^^