change httpclient dependency to >=2.6.0.1 to resolve version compatible

[ssssSoulEater]

@klehman-rally
Try to change httpclient dependency version to >=2.6.0.1

[jessejensen]

See pull request #60:
#60

[klehman-rally]

We're going to hold off on this until we complete testing on newer versions of httpclient. We have a few test failures regarding proxy handling when using httpclient v2.8.3. The hope was that we could have an entry in the gemspec file along the lines of 'httpclient', '-> 2.8' but we need to dive in and find the root cause of the proxy related tests to see if it is related to versions of httpclient subsequent to 2.6.0.1

[ssssSoulEater]

Got it, thanks for reply.