Add support for projects

[martinvanzijl]

Fixes issue #425.

Added methods:

• GitHub.getProject(int id)
• GHRepository.createProject()
• GHRepository.listProjects()
• GHOrganization.createProject()
• GHOrganization.listProjects()

Added the GHProject class.

[JosephHobbs]

I was just looking for a library specifically for interacting with projects in Github! This is great!

[geir-eilertsen]

I'm looking for this functionality as well, would be great if it was merged and released!

[bitwiseman]

Cool! We'll need tests and then I'll take another look.
@JosephHobbs @geir-origin-no
If either of you have time to write some tests please respond and that will get this change out faster.

[gskjold]

I also had use for this, so I extended @martinvanzijl contribution with columns and cards. Also added some tests, hoping they are sufficient @bitwiseman .

I'm not used to forks and how to contribute in the correct way here, but that might just be another pullreq?
Ref: https://github.com/gskjold/github-api/tree/issue_425_projects_columns_cards

[bitwiseman]

@gskjold Start a new PR and reference this one so we know to close this.

[bitwiseman]

Moving to a new PR.

[martinvanzijl]

Thanks, will delete my branch.