Broken subroute pattern

Looks like getBasePath bug.

With router definition.
`$router->get("/backend/io\.js", 'IoController@actionIndex');`

Inside Router.class
`private function patternMatches($pattern, $uri, &$matches, $flags)`

After executing with
```
var_dump($uri);
// we may have a match!
return boolval(preg_match_all('#^' . $pattern . '$#', $uri, $matches, PREG_OFFSET_CAPTURE));
```
Pattern fails with $uri.
```
string(15) "io.js"
```

Start in Router.class at patternMatches($pattern, $uri, &$matches, $flags), using the reported route `/backend/io\.js` and URI `io.js` as the reproduction. Trace how getBasePath and the subroute pattern are built, then add or update a test for this route. Done means the escaped-dot route matches the shown URI correctly without breaking other route patterns.

Written by the indexing model from the issue text.