Copyright headers still refer to GPL

[leifwalsh]

In #72 you all got consensus to relicense this project under the LGPL v3, but the headers in the source code weren't updated. Could you update them and release a new package please, to resolve any ambiguity?

[leifwalsh]

The files that need updating still seem to be these: #72 (comment)

[ssbarnea]

A PR to remove all headers would be appreviated.

[leifwalsh]

That fixes the headers, I could also change the PR to remove them. Sorry it took so long, my request for approval to contribute to this project got a bit lost and I forgot to follow up with them.