--repository does not do tilde expansion

[Jonathan Lange]

$ jitsu import --repository=~/src/pkgme-service/charms/ environment-dump.json
...
Unhandled error in Deferred:
Unhandled Error
Traceback (most recent call last):
  File "/usr/lib/python2.7/dist-packages/twisted/internet/defer.py", line 391, in errback
    self._startRunCallbacks(fail)
  File "/usr/lib/python2.7/dist-packages/twisted/internet/defer.py", line 458, in _startRunCallbacks
    self._runCallbacks()
  File "/usr/lib/python2.7/dist-packages/twisted/internet/defer.py", line 545, in _runCallbacks
    current.result = callback(current.result, *args, **kw)
  File "/usr/lib/python2.7/dist-packages/twisted/internet/defer.py", line 1095, in gotResult
    _inlineCallbacks(r, g, deferred)
--- <exception caught here> ---
  File "/usr/lib/python2.7/dist-packages/twisted/internet/defer.py", line 1037, in _inlineCallbacks
    result = result.throwExceptionIntoGenerator(g)
  File "/usr/lib/python2.7/dist-packages/twisted/python/failure.py", line 382, in throwExceptionIntoGenerator
    return g.throw(self.type, self.value, self.tb)
  File "/usr/share/juju-jitsu/sub-commands/import", line 163, in run_one
    yield func(*args, **kw)
  File "/usr/lib/python2.7/dist-packages/twisted/internet/defer.py", line 1039, in _inlineCallbacks
    result = g.send(result)
  File "/usr/share/juju-jitsu/sub-commands/import", line 69, in load
    repository = LocalCharmRepository(repo_dir)
  File "/usr/lib/python2.7/dist-packages/juju/charm/repository.py", line 44, in __init__
    raise RepositoryNotFound(path)
juju.charm.errors.RepositoryNotFound: No repository found at '~/src/pkgme-service/charms/'