Merge pull request #64 from troupe/master

Errors include a statusCode
issues now supports per_page and returns the header like stargazers
updated readme for issues per page argument
Merge pull request #65 from trevorah/master

issues can be requested with the per_page query
github url is built with url.format()
renamed method that builds the github urls
buildUrl() now supports custom query objects
issues api accepts an object of parameters. fixes #37
updated README for issues parameters
Merge pull request #66 from trevorah/master

added support for parameters in the issues api
Version bump v0.3.7
Fixes #67
Version bump v0.3.8