Inject CLI Utility

Inject is a light-weight client for the Heka client library allowing
for CLI of injecting arbitary messages into the pipeline.
Tweaked HttpInput docs for clarity and completeness.
Rename binary to heka-inject, update documentation
Represent Fields[ResponseSize] as INT. Includes documentation changes of PR593
Additional metadata for Fields
Issue #598 Prevent the sandbox externals from being installed in the DEB/RPM packages
Add User-Agent to HttpInput Requests

This will allow easier filtering of the Heka requests for the web
server.
Implement pure go ScribbleDecoder for efficiently setting message
fields to a static value.
Merge branch 'dev' into scribble-decoder
Merge pull request #590 from christianvozar/features/inject

Heka Inject CLI Utility
Merge pull request #599 from christianvozar/fixes/593-ResponseSize

Represent Fields[ResponseSize] as INT. Includes documentation changes of PR 593
Merge pull request #602 from mozilla-services/issue_598

Issue #598 Prevent the sandbox externals from being installed in the DEB...
Merge branch 'dev' into httpinput-doc-tweaks

Conflicts:
	docs/source/configuration.rst
Merge pull request #593 from mozilla-services/httpinput-doc-tweaks

Tweaked HttpInput docs for clarity and completeness.
Issue #603 Improve inject_message error message
Typo fix.
Remove Timestamp and Uuid support.
Merge pull request #605 from mozilla-services/scribble-decoder

Scribble decoder
Merge pull request #608 from mozilla-services/issue_603

Issue #603 Improve inject_message error message