Make compatible with Leaflet master

The order of events during layer initialization was changed in
Leaflet/Leaflet@bd0bc4f2e56f3ccfe8d2817e2a213b0e1480ee26, resulting
in _onMiniMapMoving being called before _lastAimingRectPosition
has been initialized.
Update Control.MiniMap.js

Localization support by using Text-attributes instead of hardcoded Text
Create Control.MiniMap-de.js

Added German Translation of Hide/Show Button Text in seprate File for easy localization
Merge pull request #23 from jfirebaugh/leaflet-master

Make compatible with Leaflet master
Update Control.MiniMap.js
Update readme.md
Merge pull request #25 from lubberscorrado/master

Localization Support of Toggle Button
Update readme.md

Cleaned up translation description a bit.
Don't clone layer objects

In general, layers aren't safe to clone -- they may contain
references to the map, to themselves, to arbitrary other objects
which should not be cloned.

The example for which cloning was added has since been removed
anyway (6afda200, c1ee4381).