add answers for first two assignments

i just add my answers on my repo. this include solutions for first two assignments with example assignment

Good to practice writing merge sort, but definitely for readability and other reasons use library functionality in real code...I see you did this with a commented out code, but here's another way to do it:

```scala
val sortedList = freqs.sortBy(_._2)
```

Why not use a map?

```scala
def makeOrderedLeafList(freqs: List[(Char, Int)]): List[Leaf] =
  freqs.map { case(c, i) => Leaf(c, i) }.sortBy(_.weight)
```
That's a lot less code! Always prefer `map`, `filter`, `reduce`, `foldLeft`, etc. when working with collections.