Avoid NPE for anonymous admin permissions check

This avoids a potential NPE when jenkins.model.Jenkins.getUser(name) ends
up calling hasPermissions for "hudson.model.Hudson.Administer".  I ran
into this on a jenkins instance that had greenballs-plugin installed, and
READ access for anonymous users enabled.

- Verify read permissions before performing anonymous authorization checks
- Make requestURI return null if Stapler.currentRequest is null
- Make currentUriPathEquals return false if requestURI is null
Depend on latest LTS plugin version
Expose getGithubApiUri to jelly
simplifying the caching code by using Guava
Merge branch 'pull-3'
Do not overwrite user's email, unless it's empty
(cherry picked from commit 88f6ee7c893bf509527df6c965e495c0d145c60c)
Merge branch 'pull-10'

Conflicts:
	pom.xml
Merge pull request #12 from ohtake/show-saved-apiuri

GitHub API URI does not show the saved value
Missing dependency in POM
[maven-release-plugin] prepare release github-oauth-0.14
[maven-release-plugin] prepare for next development iteration
Add skottler to the developer list
Merge branch 'master' into merge_cache