Build out prometheus-exporter command
Support configurable evition policies
Ignore build artifacts
Update README.md.
Move all source files existing so far to top-level.

There will be no extra CLI. This repository will (most likely) only
contain the push gateway itself, so no directory structure required.

(Having said that, there might be packages later, which would then,
obviously, go to their own directories. But the code so far is all in
'main'.)
Reimplement according to new specifications.

Unfortunately, not much of the old code could be re-used.

This is the bare-bone prototype.

In particular, there is no disk persistence yet.
And no tests...
Persisting to disk.
Added some internal metrics.
Tests for handler.go.

100% coverage!
Improved internal metrics.
Tests for storage.
Clean up lint warnings.
Switch from pat to martini.
Responses to code review.
Improve README.md.
More tweaks of README.md.
Merge pull request #2 from prometheus/feature/reimplement

Feature/reimplement