Fix the code that incorrectly trim URL.

[sifmelcara]

url.find_first_not_of("telnet://") is wrong.
Any prefix that contain characters in {'t', 'e', 'l', 'n', ':', '/'} will be removed.
For example, "eod.tw" will be trimmed to "od.tw"

[legnaleurc]

IMHO std::string::find will be better.

    const string telnetPrefix = "telnet://";
    if (url.find(telnetPrefix) == 0)
        url.erase(0, telnetPrefix.size());

[kidwm]

@legnaleurc Nice shot!
@sifmelcara how about you?

[sifmelcara]

I think substr() has better readability and speed(in worst case) in this case.
However, I do not care things other than correctness much.

[david50407]

When will this patch release?
cc @kidwm

[kidwm]

I forgot to ask @fourdollars about this yesterday