EIP191 module

[ligi]

this is the follow up of #48 (comment)

implement a module for EIP191

cc @generalpiston

[ligi]

@generalpiston - it is now released with 0.67

here an example on how you can use it: walleth/walleth@17e12d7

let me know if everything works for you!

[generalpiston]

Thank you!