Embedded special instructions about brainduck HOT 1 CLOSED

I have discussed this a bit with Mast on Code Review: http://chat.stackexchange.com/transcript/29408

It could be possible to pre-handle the code to transform non-BF characters into stuff like + - < > . , [ ] to use in Groovy (even if it might not be that clean always).

As much as possible, try to avoid using BF-chars in this code, or at least support a way to write commands without BF chars.

Additionally, #12 can check so that there are no BF-specific chars within the DSL / Groovy context.

The syntax for this is:

$ assert true

or

$ {
    assert true
}

from brainduck.