Support for multiple @ characters

[mattBrzezinski]

X-Reference from FTPClient.jl

When using multiple @ characters URIParser fails with various errors depending on the amount of @ characters passed in.

Examples:

using URIParser

URI("ftp://user@example.com:password@example.com")

> ERROR: Port must be numeric (decimal)

using URIParser

URI("ftp://user@example.com:p@ssword@example.com")

> ERROR: Port must be numeric (decimal)

using URIParser

URI("ftp://user:p@ssword@example.com")

> ERROR: Unexpected character '@' in host

[mattBrzezinski]

Current work around is to replace @ with %40, which resolves this issue.