Resolves #28

1. The code is not compiling as of now as there are errors which need to be resolved
2. All caller functions which are exposed as the client side functions have been wrapped inside go routines.
3. for H256 type I have used geth's Hash type from the common package (github.com/ethereum/go-ethereum/common.Hash)
4. Function name consistency and argument type consistency is to be ensured in the pakcages state.go , rpc.go and proof.go as functions from these are used in the execution.go file.
5. The functions dealing with Filter have not been implemented as I am not sure whether to define the filter type and all its methods ( that would be very tedious: https://github.com/gakonst/ethers-rs/blob/master/ethers-core/src/types/filter.rs). I have checked geth for something similar to the filter type but nothing found.
6. Another thing which I am unsure of is the receipt root calculation, in helios they have used an external crate (https://docs.rs/triehash/latest/triehash/fn.ordered_trie_root.html) which only takes the vector as an input and generates the root hash. I have written the function for calculating the receipt root but i am not sure of its correctness.