v2.1.0.RC4

Update UT & add wasm tools.

v2.1.0.RC3

Fix bug in write_var_uint method.

v2.1.0.RC2

1. support deserialize wasm str.
2. update UT.
3. check str len in NeoData.to_int method.

v2.1.0.RC1

1. support deploy & invoke WebAssembly(abbreviated Wasm) contract
2. Refacing Neo Vm contract interface.

v2.0.6

Add SDKException.

v2.0.5

1. Add property for InvokeFunction.
2. Add basic OEP-5 interface.
3. Fix some bugs.

v2.0.4

Fix a bug in transaction iterator.

v2.0.3

Fix a bug in build deploy transaction.

v2.0.2

• fix a serious bug in HD wallet.
• update docstring.
• refacing interface.

v2.0.1

Merge pull request #303 from NashMiao/master

update UT