Builds the Etherscan getLogs url, refs #16

Currently py-etherscan-api doesn't provide support for event logs, see:
corpetty/py-etherscan-api#26

Author: AndreMiras

src/pyetheroll.py

@@ -434,3 +434,18 @@ def get_last_bets(self, address=None, page=1, offset=100):
             }
             bets.append(bet)
         return bets
+
+    def get_logs_url(
+            self, address, from_block, to_block='latest', topic0=None):
+        """
+        Builds the Etherscan API URL call for the `getLogs` action.
+        """
+        url = self.ChainEtherscanAccount.PREFIX
+        url += 'module=logs&action=getLogs&'
+        url += 'apikey={}&'.format(self.etherscan_api_key)
+        url += 'address={}&'.format(address)
+        url += 'fromBlock={}&'.format(from_block)
+        url += 'toBlock={}&'.format(to_block)
+        if topic0 is not None:
+            url += 'topic0={}&'.format(topic0)
+        return url

src/tests/test_pyetheroll.py

@@ -511,3 +511,48 @@ def test_get_last_bets(self):
             expected_calls = [expected_call]
             self.assertEqual(
                 m_get_transaction_page.call_args_list, expected_calls)
+
+    def test_get_logs_url(self):
+        with \
+                mock.patch('etherscan.contracts.Contract.get_abi') \
+                as m_get_abi, \
+                mock.patch('pyetheroll.get_etherscan_api_key') \
+                as m_get_etherscan_api_key:
+            m_get_abi.return_value = '[]'
+            m_get_etherscan_api_key.return_value = 'apikey'
+            etheroll = Etheroll()
+        address = '0x46044beaa1e985c67767e04de58181de5daaa00f'
+        from_block = 1
+        logs_url = etheroll.get_logs_url(
+            address=address, from_block=from_block)
+        self.assertEqual(
+            logs_url,
+            (
+                'https://api.etherscan.io/api?'
+                'module=logs&action=getLogs&apikey=apikey'
+                '&address=0x46044beaa1e985c67767e04de58181de5daaa00f&'
+                'fromBlock=1&toBlock=latest&'
+            )
+        )
+        # makes sure Testnet is also supported
+        with \
+                mock.patch('etherscan.contracts.Contract.get_abi') \
+                as m_get_abi, \
+                mock.patch('pyetheroll.get_etherscan_api_key') \
+                as m_get_etherscan_api_key:
+            m_get_abi.return_value = '[]'
+            m_get_etherscan_api_key.return_value = 'apikey'
+            etheroll = Etheroll(chain_id=ChainID.ROPSTEN)
+        address = '0x46044beaa1e985c67767e04de58181de5daaa00f'
+        from_block = 1
+        logs_url = etheroll.get_logs_url(
+            address=address, from_block=from_block)
+        self.assertEqual(
+            logs_url,
+            (
+                'https://api-ropsten.etherscan.io/api?'
+                'module=logs&action=getLogs&apikey=apikey&'
+                'address=0x46044beaa1e985c67767e04de58181de5daaa00f&'
+                'fromBlock=1&toBlock=latest&'
+            )
+        )