Multi-sig ScriptSig Support

Depends on #140.
Resolves #137.
Related to #90.

The following pull request adds the following script templates to `Script`:

* `Script.createP2SHMultisigScriptSig`,
* `Script.createP2SHScriptSig`, and
* `Script.createMultisigScriptSig`

It only adds a single test for `Script.createP2SHMultisigScriptSig`, which is woeful, however it is none the less an improvement over the previous situation which had a broken implementation with no tests.

I plan on adding more tests for each of these functions as soon as possible, but this is the intermediate fix that allows for `pay-to-scriptHash` scriptSigs to be generated correctly.

The function `Script.createMultiSigInputScript` was renamed to `Script.createP2SHMultisigScriptSig`.

The test `should create valid multi-sig address` was removed because it was identical in coverage to the next test `should create valid redeemScript`.  This is because the `redeemScript` is confirmed as valid if it matches the expected `crypto.hash160(redeemScript)`.

I'd be curious to hear opinions on whether the naming convention of`*ScriptSig` and `*ScriptPubKey` is more idiomatic than the current: `*InputScript` and `*OutputScript`.
I personally find the latter misleading, but that could just be my opinion.