Interpolations at beginning of strings compile to an empty string concatenation

Any string interpolation occurring at the start of the string results in an empty string concatenation in the compiled JavaScript output.

For example:

```
"#{x}world"
```

compiles to:

```
"" + x + "world";
```

Note the empty string concatenation at the start of the output. It would be best if the compiled output was simply:

```
x + "world";
```
