Exercises from weeks 1 and 2 and first homework

These are the in class exercises and first homework.
Ah, yes. The magical `rand` method. An even cooler implementation of this is with another data type (that we haven't discussed yet), called a [Range](http://www.ruby-doc.org/core-2.1.2/Range.html). The syntax of a range looks like this:

```ruby
range = 1..10
```

Which would allow you to do something like this:

```ruby
range = 1..10
secret_number = rand(range)
```

Ranges also have some cool methods like `to_a` which will give you each element of the range:

```ruby
range = 1..10
range.to_a
#=> [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]
```