(NC-111) Add `expand-seq-params` utility.

This utility relieves the tedium of using sequential SQL parameters in
prepared statements (e.g. with an `IN` clause) by expanding each
sequential parameter's placeholder in the prepared statement SQL to be
an SQL list literal with the appropriate number of `?`s given the length
of the sequential parameter.

For example:
  ["SELECT * FROM kerjiggers WHERE name IN ?" ["bob" "carol" "eve"]]
becomes
  ["SELECT * FROM kerjiggers WHERE name IN (?,?,?)" "bob" "carol" "eve"]
(NC-111) Add annotate-group Storage method.

This method takes a group and returns its annotated version, which marks
classes and parameters that have been deleted from puppet. If the group
has no references to deleted classes or paremeters, the annotated
version is equal to the normal representation.
(NC-111) Return annotated groups from endpoints.

Whenever a group or groups would be returned to the user in a 200
response, they are annotated first to mark deleted class or class
parameters that the group references.

This does not happen for groups that are returned with a 201 response,
but since this only happens when the user is creating the group with
a PUT, and all the classes & parameters of the group are checked before
it is created, it should not be an issue.

Update API docs for groups to describe the annotations and provide an
example of an annotated group.
Merge pull request #50 from aperiodic/nc-111-annotate-deleted

(NC-111) Annotate deleted classes & parameters of groups.