unit spec for query mapper examples
convert nil to "", e.g. an empty key, prevents error with `dup`
Add license statement as required.

 Ansgar Burchardt noticed missing license statements http://lists.alioth.debian.org/pipermail/pkg-ruby-extras-maintainers/2013-July/015499.html
Add license statement as required.
add license to version_checker.rb
HTTP Gem support
Limit excon dependency version
Play nice with excon >= 0.29.0
Bump minimal version of excon to 0.27.5

Resolves #347
Merge pull request #352 from JonRowe/fixup_query_mapper

Fix issue where empty query key causes a `TypeError`
Merge pull request #357 from vid-io/fix/excon-dependency

Limit excon dependency version
Merge pull request #356 from vid-io/feature/http-gem-support

HTTP Gem support
Version bump to 1.17.0
Merge pull request #355 from pravi/patch-1

Add license statement as required.
Version bump to 1.17.1