Improve color provider

[malefice]

What does this changes

This will add a new color provider method color() that allows specifying a hue, a luminosity, and a color format to generate an matching color.

>>> from faker import Faker
>>> fake = Faker()

# Create random blue color in RGB format
>>> fake.color(hue='blue', color_format='rgb')
'rgb(5, 56, 175)'

# Create random bright red color in HSV format
>>> fake.color(hue='red', luminosity='bright', color_format='hsv')
'hsv(345, 96, 90)'

# Create random light pink color in HSL format
>>> fake.color(hue='pink', luminosity='light', color_format='hsl')
'hsl(294, 93, 71)'

# Create random color from yellow to green spectrum in hex format
>>> fake.color(hue=[50, 120], luminosity='dark', color_format='hex')
'#3f7c02'

What was wrong

There is currently no support for such features.

Notes

Personally, I prefer to return tuples of HSV, HSL, and RGB values instead of the color_format(X, Y, Z) string notation or any string for that matter, so that there is no need for users to parse the string for the values. I followed the current way rgb_color() and rgb_css_color() do this, but I am not a fan of those methods.

I also think that it would be better to provide more convenient methods and update old ones, so users will not need to remember the different color_format values while still being able to just specify 'blue' and 'dark' to get a color of that type.

Fixes #104

[fcurella]

isn't this equivalent to s_max = lower_bounds[-1][0]?

[malefice]

You are right. I wonder why the author of randomcolor-py did not just use [-1] for this one. I will fix this, and I am sorry I did not notice.

[fcurella]

can we also show the value itself in the exception message? Something like 'Value of hue `%s` is invalid.' % hue

[malefice]

This should only happen if something is wrong with COLOR_MAP itself, but sure.

[fcurella]

I'm not sure I'd want it to silently fallback to defaults. I'd rather have it throw an exception if the user is passing invalid values.

[malefice]

Alright, I will change this behavior.

[malefice]

The flake8 errors are related to PR #1058.

[fcurella]

Looks Good! Thank you so much!