Unsatisfiable query options

[pilaf]

@marquete @turino

This PR adds an option that affects the way the library behaves when dealing with unsatisfiable queries:

FmRest::Spyke.on_unsatisifiable_query = :return_silent
Contact.query(first_name: "Jacob").and(first_name: "marquete")
# => [] (no Data API request sent)
Contact.query(first_name: "Jacob").and(first_name: "marquete").or(first_name: "Jacob")
# -> issues a Data API request with first_name: "Jacob"

FmRest::Spyke.on_unsatisifiable_query = :request_silent
Contact.query(first_name: "Jacob").and(first_name: "marquete")
# -> issues a Data API request with first_name: "1001..1000"

FmRest::Spyke.on_unsatisifiable_query = :raise
Contact.query(first_name: "Jacob").and(first_name: "marquete")
# -> UnsatisfiableQuery error

Other options not showcased above are :return_warn and :request_warn, which will do the same as the first two examples, but also printing a warn() message.

This is missing updated specs and documentation, but I'd like your general input.

[marquete]

Looks great!