Add GPOS resource record support.

Add GPOS to generic.rb, implement encode_rdata and decode_rdata.

Break up long lines into several smaller lines.

Add ;nil note.

Fix decoding/encoding of lat/long/alt.  Add GPOS test to ts_offline. Add dev dependencies pry, ripl.

Skeletal test code no longer fails.

Restructured based on RR superclass assumptions, currently tests fail.

Remove to_s, inspect, initialize (handled by superclass). Add owner alias for name. Tests passing again.

Corrected arg order; longitude comes before latitude.

More tests.

Added test_to_s.  Added but disabled test_hash.

Clean up tests, but still under construction.

In GPOS: populate rdata in from_hash. Add class method for building rdata. Add test_populates_rdata.
Add sample zone file content as comment to test file.
Make minor improvement to CodeMapper init error message.

Add class methods from_hash, from_string, from_data to instantiate GPOS records.

Fix order of long, lat in error message.