Table alignment in functional/index.md (#152)

* Right align table in plain text version
  Makes the plain text version easier to read

* Center alignment in mdbook/md

functional/index.md

@@ -15,7 +15,7 @@ println!("{}", sum);
 With imperative programs, we have to play compiler to see what is happening. Here, we start with a `sum` of `0`. Next, we iterate through the range from 1 to 10. Each time through the loop, we add the corresponding value in the range. Then we print it out.
 
 | `i` | `sum` |
-| --- | ----- |
+|:---:|:-----:|
 |   1 |     1 |
 |   2 |     3 |
 |   3 |     6 |
@@ -40,7 +40,7 @@ Whoa! This is really different! What's going on here? Remember that with declara
 Here, we are composing functions of addition (this closure: `|a, b| a + b)`) with a range from 1 to 10. The `0` is the starting point, so `a` is `0` at first. `b` is the first element of the range, `1`. `0 + 1 = 1` is the result. So now we `fold` again, with `a = 1`, `b = 2` and so `1 + 2 = 3` is the next result. This process continues until we get to the last element in the range, `10`.
 
 | `a` | `b` | result |
-| --- | --- | ------ |
+|:---:|:---:|:------:|
 |   0 |   1 |      1 |
 |   1 |   2 |      3 |
 |   3 |   3 |      6 |