Don't encode addr in normalize_msisdn.
Re-factor normalize_msisdn tests into their own class and separate methods.
Add test that unicode and str addresses are not encoded or decoded.
Merge branch 'develop' into feature/issue-796-dont-encode-addr-in-normalize-msisdn
Merge branch 'feature/issue-796-dont-encode-addr-in-normalize-msisdn' into develop