Add composer.json and relocate `Lckamal\Navigation\NavigationComposer` to follow PSR-0.

Signed-off-by: crynobone <crynobone@gmail.com>
Update installation guide.

Signed-off-by: crynobone <crynobone@gmail.com>
Merge pull request #2 from crynobone/patch/composer

Add composer.json and relocate `Lckamal\Navigation\NavigationComposer` to follow PSR-0.