Add SFINAE restrictions for T_COLOR_FEATURE, T_METHOD, T_GAMMA

[jeffreyabecker]

Is your feature request related to a problem? Please describe.
My IDE is very very lost when it comes to code completion / checking on T_COLOR_FEATURE, T_METHOD, T_GAMMA. SFINAE restrictions would let IDE's do method / type inference correctly.

Describe the solution you'd like

• Create C++11 compatible SFINAE type restriction declarations
• Use them wherever the templates are declared

Describe alternatives you've considered
Maybe there's something that could be done with doxygen comments?

Additional context
I can put together a PR if desired.

[jeffreyabecker]

update: example branch here:
https://github.com/jeffreyabecker/NeoPixelBus/tree/SFINAE

[Makuna]

Unfortunately, not all platforms support C++11 yet. Some platforms don't even have STD library.

So these would have to be wrapped up in a such a way to be empty statements for those platforms and make sure the STD is only used on platforms that have it.