YobiUpdate: Do not check update so frequently

By the default, Yobi checks whether new software update is available
every a millisecond. This is a bug of the configuration library to
interpret 1d as 1ms. See
https://github.com/typesafehub/config/issues/117 for detail of the bug.
YobiUpdate: Fix incorrect update site

The default update site has changed to repo.yobi.io in
application.conf.default since 5a9e026 but it should be also changed in
app/models/YobiUpdate.java.
Merge branch 'fix/check-update-too-frequently' of dlab/hive

from pull-request 1406

* refs/heads/fix/check-update-too-frequently:
  YobiUpdate: Fix incorrect update site
  YobiUpdate: Do not check update so frequently

Reviewed-by: 백기선 <keesun.baik@navercorp.com>
Upgrade JGit to 3.5.3 to fix vulnerability

Fix a critical security vulnerability which affects to OSX and Windows
users.

See https://github.com/blog/1938-git-client-vulnerability-announced for
more details about the vulnerability.
Merge branch 'fix/jgit-cve-2014-9390' of dlab/hive

from pull-request 1408

* refs/heads/fix/jgit-cve-2014-9390:
  Upgrade JGit to 3.5.3 to fix vulnerability

Reviewed-by: 김덕홍 <insanehong@navercorp.com>
Add the release note for v0.7.3
Merge branch 'docs/relnotes-0.7.3' of dlab/hive

from pull-request 1407

* refs/heads/docs/relnotes-0.7.3:
  Add the release note for v0.7.3

Reviewed-by: 김덕홍 <insanehong@navercorp.com>
Yobi 0.7.3

A critical security vulnerability of JGit and a bug to check update too
frequently was fixed.

Reviewed-by: insanehong <insane.hong@navercorp.com>