Documentation Update - tl.layers.clear_layers_name()

[DEKHTIARJonathan]

Dear Tensorlayers,

I would like first of all to thank you for this outstanding work. Really helped a lot.

It took me two days of work to diagnose a problem I had.
I tried resetting the current graph and trying to redefining it, nothing I was doing was working until I found this function hidden in the tensorlayer library: tl.layers.clear_layers_name().

Maybe, tl.layers.clear_layers_name() automatically triggered when the default graph is changed, at least it should be mentioned and highlighted in the documentation. I really wasted many hours trying to figure this out.

[zsdonghao]

Thank you for your advise, I will update it now, please let me know or submit a PR if you find my edition is not good enough.

BTW, #214 this issue may also helpful for you

[DEKHTIARJonathan]

Seems good enough, maybe you should modify the raise error:

I will open a PR with a change "proposal" for the error raised: #290

Current Exception:

Exception: Layer 'my_layer_name' already exists, please choice other 'name' or reuse this layer
Hint : Use different name for different 'Layer' (The name is used to control parameter sharing)

Proposed Exception:

Exception: Layer 'my_layer_name' already exists, please choice other 'name' or reuse this layer
Hint : Use different name for different 'Layer' (The name is used to control parameter sharing)
Additional Informations: http://tensorlayer.readthedocs.io/en/latest/modules/layers.html?highlight=clear_layers_name#tensorlayer.layers.clear_layers_name

@zsdonghao I close this one, I think we don't need more info, if you wan't to discuss about this one, I stay available on #290

Thanks a lot for your help and once again: very nice work !

Jonathan