Remove adaptive breakpoints from gallery, make it flexible

Such bigness

![screen shot 2014-08-14 at 14 37 35](https://cloud.githubusercontent.com/assets/271645/3920619/52a395b2-23b8-11e4-9697-95a75a0cdf98.png)

Such smallness

![screen shot 2014-08-14 at 14 37 49](https://cloud.githubusercontent.com/assets/271645/3920614/4d7af846-23b8-11e4-887a-016d53a5ef65.png)


Didn't you make a mixin for aspect-ratio?