Move to LGPL 3.0

[karussell]

You should move on to LGPL version 3 as version 2 is incompatible with Apache License.

And because the license text says: "either version 2.1 of the License, or (at your option) any later version." this should be a no brainer.

[Rob Eden]

From the original author:

I see no point in upgrading. Those who want to use lgpl3 can. Those who do not, aren't forced to. Everybody wins. This seems to be a stance some other projects have taken as well.