Added geturl() method

[zmej-serow]

Type of changes

• Bug fix
• New feature
• Documentation / docstrings
• Tests
• Other

Checklist

• I've run the latest black with default args on new code.
• I've updated CHANGELOG.md and CONTRIBUTORS.md where appropriate.
• I've added tests for new code.
• I accept that @willmcgugan may be pedantic in the code review.

Description

A new method to get URL for FTP resource.
For example,
ftp://127.0.0.1/foo
ftp://127.0.0.1/foo/bar

[coveralls]

Coverage decreased (-0.7%) to 98.924% when pulling c472c06 on zmej-serow:patch-1 into 9c92da1 on PyFilesystem:master.

[coveralls]

Coverage decreased (-0.7%) to 98.924% when pulling c472c06 on zmej-serow:patch-1 into 9c92da1 on PyFilesystem:master.

[coveralls]

Coverage decreased (-0.7%) to 98.924% when pulling c472c06 on zmej-serow:patch-1 into 9c92da1 on PyFilesystem:master.

[coveralls]

Coverage increased (+0.0003%) to 99.613% when pulling c472c06 on zmej-serow:patch-1 into 9c92da1 on PyFilesystem:master.

[lurch]

Sorry for coming late to the party... should this method (or the self.ftp_url method) also take username (if not 'anonymous'), proxy (if not None) and password (if not '') into account?

[willmcgugan]

Good point. @zmej-serow what do you think?

[zmej-serow]

@lurch, nice idea!
Will definitely take a look tomorrow.