Remove superfluous context.path

It was generating URLs that look like
http://server.example.com/gitbucket/gitbucket/git/user/repo.git (notice
the extra "/gitbucket"?) when the WAR was deployed in Tomcat.
Resolves error when deleting repsository with PR.
Fetch pull request from source repository after updating repository.
Merge pull request #202 from odz/delete-repository-with-pullreq

Resolves Error when deleting repository which has PR.
Merge pull request #203 from olivierdagenais/FixManualMergeUrls

Remove superfluous context.path
Ignore TransportException if the source branch had been removed.
Ignore Exception instead of TransportException
Merge branch 'pullreq-update-in-push' of https://github.com/odz/gitbucket into odz-pullreq-update-in-push

Conflicts:
	src/main/scala/app/PullRequestsController.scala
(refs #211)README.md detection is case insensitive and it also detect README.markdown as same as Github.
(refs #204)Add some way to configure data directory.

1) system property of JVM (e.g. -Dgitbucket.home=PATH_TO_DATADIR)
2) java -jar gitbucket.war --data=PATH_TO_DATADIR
3) Add context parameter "gitbucket.home" to web.xml
(refs #204)Change the option name from --data to --gitbucket.home