Add support for phone numbers with extensions

[jerryclinesmith]

Requested in issue #57 and #78, this pull request adds support for phone numbers with extensions.

Leveraging some code from the "phone" gem, I'm basically extracting the extension, running the normal code using Phony, then adding the extension back at the end.

"+31 (0)30 1234 123 x999".phony_normalized # => '31301234123 x999'
"+31 (0)30 1234 123 ext999".phony_normalized # => '31301234123 x999'
"+31 (0)30 1234 123 #999".phony_normalized # => '31301234123 x999'

I think there could be more options around formatting, but wanted to gauge interest in accepting the changes first.

[coveralls]

Coverage decreased (-0.2%) to 99.76% when pulling 9e69742 on jerryclinesmith:extension-support into cfb90f5 on joost:master.

[coveralls]

Coverage decreased (-0.2%) to 99.76% when pulling 42968fa on jerryclinesmith:extension-support into cfb90f5 on joost:master.

[coveralls]

Coverage decreased (-0.2%) to 99.76% when pulling 4442e8e on jerryclinesmith:extension-support into cfb90f5 on joost:master.

[coveralls]

Coverage decreased (-0.2%) to 99.762% when pulling 08e7445 on jerryclinesmith:extension-support into cfb90f5 on joost:master.

[coveralls]

Coverage decreased (-0.2%) to 99.762% when pulling 6f27842 on jerryclinesmith:extension-support into cfb90f5 on joost:master.

[coveralls]

Coverage remained the same at 100.0% when pulling b442c72 on jerryclinesmith:extension-support into cfb90f5 on joost:master.

[coveralls]

Coverage remained the same at 100.0% when pulling ada7e6e on jerryclinesmith:extension-support into cfb90f5 on joost:master.

[joost]

Seems supernice also. Also here.. we should add your pull request text to the README.

[jerryclinesmith]

Comments added, glad to see it pulled in! Thanks

[joost]

Sorry, your other PR introduced some conflicts :| :)

[jerryclinesmith]

Should be fixed now...

[coveralls]

Coverage remained the same at 100.0% when pulling a3da999 on jerryclinesmith:extension-support into 337f886 on joost:master.