feature: min

[LinusU]

fixes #174

This add a new feature .min() which preserves the aspect ration and resize the image to the minimum width or height specified.

On another note, we might want to make the documentation for max() and min() a bit clearer. This is how Mozilla describes the background-size values contain and cover:

cover
This keyword specifies that the background image should be scaled to be as small as possible while ensuring both its dimensions are greater than or equal to the corresponding dimensions of the background positioning area.

contain
This keyword specifies that the background image should be scaled to be as large as possible while ensuring both its dimensions are less than or equal to the corresponding dimensions of the background positioning area.

I think that if we draw some inspiration from here we can make it a bit more clear what they do. @lovell?

[LinusU]

The Snap CI build fails because of c7ccf68, I don't think that I can be blamed for that :)

[coveralls]

Coverage increased (+0.03%) to 97.51% when pulling bcd82f4 on LinusU:feature-min into 749dc61 on lovell:master.

[lovell]

This is a perfect patch, favour fortunes the brave, thank you!

Good call on simplifying the docs - leave it with me.

Snap CI is failing as it only provides gcc 4.4 by default and therefore isn't fully C++11 compatible. I've updated the environment to manually install gcc 4.7 each time but it doesn't seem to apply to Pull Requests.

[LinusU]

Thanks for quick pull! 🍻

Would appreciate it if you could publish this as 0.9.4 to npm :)

[lovell]

v0.9.3 will be published within the next hour - currently fixing CI environment problems.

[LinusU]

Understandable, thanks! I appreciate it

[lovell]

All done, enjoy!