Add support for multiline comments above property

[Silthus]

Regarding #51 it would also be very helpful to allow comments above a property to be parsed for the schema tags.

For example:

# My description of this really cool property.
@ @schema title:"My Property"
# @schema maxLength:10;pattern:^[a-z]+$
my_property: some value

The above also defaults a non annotated comment above a property to use as the description. Maybe this could be turned on with a flag in the cli?