Introduce decorator-style API

Decorators are pretty?

For example (name is undecided), we can simply define a decorated “op builder” function:

@tfplot.op(batch=True)
def plot_heatmap(heatmap, cmap='jet')
    # heatmap: a [16x16] numpy array here
    fig, ax = tfplot.subplots(figsize=(4, 3))
    im = ax.imshow(heatmap, cmap=cmap)
    fig.colorbar(im)
    return fig

# heatmap_tensor : a float32 Tensor of shape [4, 16, 16], for example
>>> plot_heatmap(heatmap_tensor)
Tensor("PlotHeatmap:0", shape=(4, ?, ?, 3), dtype=uint8)

Instead of:

# heatmap_tensor : a float32 Tensor of shape [4, 16, 16], for example
>>> PlotOp = tfplot.wrap(figure_heatmap, batch=True, name='PlotHeatmap')
>>> PlotOp(heatmap_tensor)
Tensor("PlotHeatmap:0", shape=(4, ?, ?, 3), dtype=uint8)

[wookayin]

I have been working on this these days, please see #7 (in progress).

• tfplot.wrap: The existing tfplot.wrap() can be used as a decorator as well, as suggested by @ferrine.
• tfplot.autowrap: Similar to wrap, but supports automatic injection of fig, ax. This will replace wrap_axesplot soon. Batch supports, etc. will be added soon.

/cc @ferrine Do you want to take a look or review it?

[wookayin]

If you want to kindly give some suggestions, it would be greatly appreciated of course.