add second parameter to getParentWhile condition

[Validark]

Builds off: #107

Being able to call node.getParentWhile(p => ts.TypeGuards.etc(p) || etc) is very nice. However, I would like to be able to easily check whether the node under it has the proper relationship to the current parent. For example, let's say I want to figure out whether something is in the conditional of an if statement:

node.getParentWhile((p, n) => ts.TypeGuards.isIfStatement(p) && p.getExpression() === n)

Where:

• n is the current node which starts as node in the above example
• p is the current parent which starts as node.getParent() in the above example

[dsherret]

@Validark that sounds like a good idea. Would you like to implement it? If not, I'll get to it sometime soon.