Mobile friendly, and add some styles

- Changes (a bit) the README.
- Adds sprockets.
- Adds sass.
- More mobile friendly.
- Adds some heroku styles.

**New Guest view**
![](http://cl.ly/image/2J2C2j3j1613/content)

**Adding new guests**
![](http://cl.ly/image/132x3S2r1l3c/content)

**Guest list**
![](http://cl.ly/image/3g2U3t1V132H/content)

**Stats**
![](http://cl.ly/image/0S1X3O1E251w/content)

**Edit Guest view**
![](http://cl.ly/image/1M082p0Y3T0I/content)

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This is not 100% completed, but it's something. The current layout could be improved for mobile devices, but at least now it's easier to use (IMO).