| Q             | A
| ------------- | ---
| Bug fix?      | yes
| New feature?  | no
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets | #177
Updated PhoneNumber::validate to explicitly reject inputs containing alpha characters.
Prevents libphonenumber from parsing "vanity numbers" or ignoring trailing alpha characters.
Added regression tests for the reported cases.