Update to 3.0.1, the main highlights of this release are Segregated Witness
(segwit) support and has switched from qt4 to qt5.

Cold storage wallet support still need some work. Therefore disable the trezor
and ledger support for now until things have been fixed.

Users depending on trezor and ledger are advised to use finance/electrum2 for
the time being.

Changelog: https://github.com/spesmilo/electrum/blob/master/RELEASE-NOTES