Fix a bug where user can enter word not from Electrum list.

[yangit]

Here is a fix to an issue where user can enter non Electrum words and still be able to operate his wallet. This addresses issue #12 and #13 This update increases security, however it is a breaking change for users whose security is already affected.

I can come up with error message notification for affected users if you wish so.

[ghost]

Not sure if someone ever thanked you, Yan, but thank you.

Cheers.

[yangit]

:) Thanks!