change URL to `https://crates.io/<author>/<crate>`

[liigo]

change URL to https://crates.io/<author>/<crate>, end with an optional /<database_id>.

for example, the current url:
https://crates.io/crates/time
will be changed to:
https://crates.io/alexcrichton/time
and https://crates.io/alexcrichton/time/123

• not repeat crates two times in one URL
• author's name to distinguish different crates with the same name, like github
• optional id to speed up the database searching
• the page https://crates.io/<author> list his/hers created and favorite crates.

(There are already several time crates, and several sqlite3 crates, in the github, I don't think only one of them be named the best time/sqlite3, and others must be named different such as time2/sqlite3-liigo, to make the crate name unique all over the crates.io.)

[liigo]

@alexcrichton

[huonw]

Placing the author name at the top-level would require we disallow certain account names to allow crates.io to have its own pages e.g. https://crates.io/install , https://crates.io/crates and https://crates.io/me would presumably mean that https://github.com/install , https://github.com/crates and https://github.com/me could not have accounts on crates.io.

This would also restrict what pages can be added in future.

It may not be a huge problem, but it's something that should be considered.

[huonw]

In any case, allowing multiple crates with the same name is not as simple as making the URL structure compatible, see e.g. #58 or rust-lang/cargo#975 .

[alexcrichton]

In the interest of adding new routes in the future, we must have a prefix somehow (as @huonw mentioned), and otherwise I'm going to close this as a dupe of the issues @huonw mentioned.