#300 escape all values going into compile Dust code to allow for //

Buffers, raw, literal, references etc were only going through JSON.stringify. 
They should be js escaped instead. Dust's jsescape escapes slahes and other stuff.


Issue #300 would affect places were literals, buffers or raw are used, but buffers are the most to be a problem.

for a template:
```
// inline comments
```

we want the compiled template to write
```
chk.write("\/\/ inline comments")
```

similarly  there are cases where you'll have

```
{#section param="//comment?"}
{/section}
```

```
{>"//comment"}
```


```
{`
raw blocks of code
with // comment
`}
```