geoserver_seeder: a total rework

 * implementing tile generation in ruby (same floating point logic as js)
 * all arguments can be controlled from command line
 * takes a sample url for operation
 * broken nicer into classes
 * fix thread joining
 * support contacting geonetwork on https
unit tests for geoserver seeder
geoserver_seeder: adjust optimal number of threads

for small workloads, do not spawn many threads
geoserver_seeder: imitate js behaviour for rounded floats

chop .0 when calculating bounding boxes
rename tile_seeder -> geoserver_seeder
use rspec instead of minitest for testing
geoserver_seeder: minor corrections

 * run only one zoom level if end zoom level undefined
 * never return 0 number of threads for operations
 * fix help message accordingly
geoserver_seeder: add Gemfile
Merge pull request #16 from aodn/geoserver_seeder_rework

geoserver seeder rework