Various fixes and formatting chores (#885)

* fix: clean up solium linting errors

* fix: make various contracts natspec compliant

* fix: this.balance deprecated; convert to address(this).balance

* fix: contract.call deprecated and switch to gasleft()

* fix: ignore empty block rule project-wide

* fix: add ignore cases for the rest of the linting warnings

contracts/Bounty.sol

@@ -43,7 +43,7 @@ contract Bounty is PullPayment, Destructible {
     require(researcher != 0);
     // Check Target contract invariants
     require(!target.checkInvariant());
-    asyncSend(researcher, this.balance);
+    asyncSend(researcher, address(this).balance);
     claimed = true;
   }