Double curly brackets in comments cause style ruining

[thybzi]

Comments of specific kind in source CSS become broken after applying bless, ruining surrounding styles.

this code:

.previous-block {
    [...]
}

/* My block {{ */
.my-block {
    [...]
}
/* }} My block */

becomes:

.previous-block {
    [...]
} */
.my-block {
    [...]
}
/* }} My block */

[aabenoja]

Reported in #24, will be resolved in v4.