Stop pinning webcomponentsjs version
Stop pinning webcomponentsjs version

Polymer seems to have made a mistake in releasing webcomponentsjs v0.6.2
and has released v0.6.3 which is identical to v0.6.1.  We no longer need
to pin our version at v0.6.1.

Fixes #1585

MinFu/uproxy,MinFu/uproxy,jpevarnek/uproxy,jpevarnek/uproxy,qida/uproxy,IveWong/uproxy,IveWong/uproxy,dhkong88/uproxy,jpevarnek/uproxy,itplanes/uproxy,qida/uproxy,jpevarnek/uproxy,MinFu/uproxy,uProxy/uproxy,chinarustin/uproxy,dhkong88/uproxy,IveWong/uproxy,chinarustin/uproxy,chinarustin/uproxy,qida/uproxy,roceys/uproxy,roceys/uproxy,itplanes/uproxy,qida/uproxy,itplanes/uproxy,MinFu/uproxy,chinarustin/uproxy,IveWong/uproxy,dhkong88/uproxy,qida/uproxy,uProxy/uproxy,roceys/uproxy,itplanes/uproxy,jpevarnek/uproxy,roceys/uproxy,dhkong88/uproxy,roceys/uproxy,dhkong88/uproxy,chinarustin/uproxy,uProxy/uproxy,uProxy/uproxy,itplanes/uproxy,MinFu/uproxy,uProxy/uproxy