message: Update: Common Wallet Interface `sign` method docs
diff: @@ -328,25 +328,31 @@ transactionObject {
  gasLimit: bigNumber // The gas limit you want for this transaction, as an instance of bigNumber. Defaults to 21000
  chainId: Number // The chain id where the transaction is going to be sent. Defaults to 1.
  nonce: Number // The nonce of the transaction. Defaults to 0.
  - to: String // The destination address to send the transaction to, as a hex String. This is the only REQUIRED prop by this library
  + to: String // The destination address to send the transaction to, as a hex String. If you deploy a new contract, you must omit this prop.
  value: bigNumber // The value you want to send to the destination address, in WEI, as an instance of bigNumber. Defaults to 1 WEI
  - inputData: String // The additional input data to send in the transaction, as a hex String. Defaults to `0x00`
  + inputData: String // The additional input data to send in the transaction, as a hex String. Defaults to ''
  }
  ```
  +**Contract deployment:**
  +
  +To create and then sign a transaction intended to deploy a contract you need to omit the destination address field _(`to` prop)_. The sign method expects this and will not validate against it.
  +
  +_**Note**: While all other wallet types allow you to pass in an empty `inputData` field (not that it would be very useful), Trezor requires you to specifically set it. So you won't be able to sign a contract deployment transaction without also setting the transaction data._
  +
  **Usage:**
  ```js
  -import { open } from '@colony/purser-trezor';
  +import { open } from '@colony/purser-software';
  -const trezorWallet = await open();
  +const softwareWallet = await open({ mnemonic: 'load blush ... sheriff surge' });
  -const transactionSignature = await trezorWallet.sign({ to: '0x3953...a4C1' }); // 0xF990...8d91
  +const transactionSignature = await softwareWallet.sign({ to: '0x3953...a4C1' }); // 0xF990...8d91
  ```
  ```js
  -import { open } from '@colony/purser-trezor';
  +import { open } from '@colony/purser-ledger';
  import { bigNumber } from '@colony/purser-core/utils';
  -const trezorWallet = await open();
  +const ledgerWallet = await open();
  const transaction = {
  gasPrice: bigNumber('0.00000001').toWei(),
  @@ -358,7 +364,21 @@ const transaction = {
  inputData: '0x00',
  };
  -const transactionSignature = await trezorWallet.sign(transaction); // 0xf849...5681
  +const transactionSignature = await ledgerWallet.sign(transaction); // 0xf849...5681
  +```
  +Deploy a contract:
  +```js
  +import { open } from '@colony/purser-trezor';
  +import { bigNumber } from '@colony/purser-core/utils';
  +
  +const trezorWallet = await open();
  +
  +// omit the 'to' prop
  +const newContractTransaction = {
  + inputData: '0x00',
  +};
  +
  +const transactionSignature = await trezorWallet.sign(newContractTransaction); // 0xf849...993a
  ```
  ### `signMessage()`
  