simplify trie, and support delete unused storage
save
remove unused strorage when updating
clear storage when clear trie
follow the same name convension with yellow paper
use property for root hash again to prevent problems by set hash directly
some fixes
fix: initialization
remove unused method
cache blank account as template
Replace optparse with argparse, fixes #79

This replaces the optparse module in `eth.py` with argparse.
The "verbosity" cli-option became `-V` to avoid clashing with
the builtin `-v` == `--version` option.
Don't create dependent scripts

Buildouts `bin/`-directory got pretty cluttered from all the
dependent console-scripts. The core console-scripts should be
enough for what we want.
Do fully-qualified import

Using `eth.py` with the buildout-bundled python
interpreter like `bin/python pyethereum/eth.py` failed, because
the import of common was not qualified.
add: tips4commit in readme
revert: regression brought in commit# 5e6c7a4c73e222859fcd7dd84c95ee077883c821
Add missing dependency to requirements.txt, fix #95
fix: #99
fix: db instances must share uncommitted dict
fix: failing transaction test
additional transaction tests