doc: markdown stubs: sending_data, widgets, hacking

Hacking

-------

here be dragons

### Writing custom widgets / views

here be dragons

Sending Data

------------

FnordMetric operates on an input stream of "events". These events are JSON

objects (arbitrary hashmaps). A event may look like this:

    { "_type": "sale", "product_id": 534221, "purchase_value": 2999 }

There is a small number of keys which have a special meaning, all of them

are prefixed with an underscore:

    fixpaul: special key table

You can choose between a variety of ways to submit these events to FnordMetric:

### HTTP API

here be dragons

### TCP / UDP API

here be dragons

### Redis API

here be dragons

### AMQP

here be dragons

### STOMP

here be dragons

Widgets

-------

FnordMetric includes a collection of UI widgets to display gauge data. You

can use these widgets with a simple ruby DSL.

_Example: Render a timeseries line chart on dashboard "Sales"_

    widget 'Sales',

      :title => "Sales per Minute",

      :gauges => [:sales_per_minute],

      :type => :timeline,

      :width => 100

### TimelineWidget

here be dragons

### NumbersWidget

here be dragons

### BarsWidget

here be dragons

### ToplistWidget

here be dragons

### HTMLWidget

here be dragons

High-Level Widgets

------------------

There are a few high level widgets which have different semantics. FIXPAUL: explain...

### TimeSeriesGauge

here be dragons

### DistributionGauge

here be dragons

### ToplistGauge

here be dragons