Make modern gem build not complain

[ripienaar]

Building with new rubygems raises all kinds of issues

>>> Building travlrmap-1.3.0.gem ...
WARNING:  licenses is empty, but is recommended.  Use a license abbreviation from:
http://opensource.org/licenses/alphabetical
WARNING:  open-ended dependency on sinatra (>= 0) is not recommended
  if sinatra is semantically versioned, use:
    add_runtime_dependency 'sinatra', '~> 0'
WARNING:  open-ended dependency on bundler (>= 0) is not recommended
  if bundler is semantically versioned, use:
    add_runtime_dependency 'bundler', '~> 0'
WARNING:  open-ended dependency on httparty (>= 0) is not recommended
  if httparty is semantically versioned, use:
    add_runtime_dependency 'httparty', '~> 0'
WARNING:  open-ended dependency on ruby_kml (>= 0) is not recommended
  if ruby_kml is semantically versioned, use:
    add_runtime_dependency 'ruby_kml', '~> 0'