Initial support for existence of a `base_dir` global config option, defaulting to
`/var/cache/hekad`.
Merge branch 'dev' into features/heka-root-folder
Merge branch 'dev' into features/heka-root-folder

Conflicts:
	pipeline/config.go
Significant changes to seek journal configuration behavior for LogfileInput and
LogfileDirectoryManagerInput, w/ corresponding changes to documentation and
tests.
Tweaks to whisper output code and docs to support output dir relative to the Heka
base dir.
Update DashboardOutput code and docs to make use of Heka base dir.
Merge branch 'dev' into features/heka-root-folder

Conflicts:
	cmd/hekad/config.go
	cmd/hekad/main.go
Merge typo.
Clarify that a LogfileInput is only created when a matching log file is found, not an
empty directory.
Typo.
Update changelog.
Helps to make sure folders have the +x bit set. :P
Merge branch 'dev' into features/heka-root-folder

Conflicts:
	CHANGES.txt
Merge pull request #380 from mozilla-services/features/heka-root-folder

Features/heka root folder, resolves #331.