Impress sessions refactored

* client.session - > client.sid
* client.application.sessions[client.session] -> client.session
Examples fixed
Refactored impress.security

* Refactored .register() .signIn(), .signOut()
* sessionCreated and sessionModified moved to Client class from session
hash
* Examples fixed
Merge master to session
Session cookie secret, close issue #89
Merge pull request #101 from tshemsedinov/master

Changes from master branch
Merge pull request #108 from tshemsedinov/master

Changes from master branch
Update README.md
Version 0.1.87

* Deprecated /config/databases.js parameter: database.alias, use hash
key instead
* Sandbox namespaces are arranged, see issue for details, close #102
* Warning: you need refactor code, replacing fs.*, async.*, ... to
api.fs.*, api.async.*, ...
Code style fixes
Merge remote-tracking branch 'origin/master' into session

Conflicts: lib/impress.sse.js
Merge branch 'session' of https://github.com/tshemsedinov/impress into session
Merge pull request #110 from tshemsedinov/session

Session branch
Version 0.1.88

* Impress sessions refactored
* client.session - > client.sid
* client.application.sessions[client.session] -> client.session
* Refactored impress.security.js (according to session changes)
* Fixed examples (to comply new session changes)
* Refactored .register() .signIn(), .signOut()
* Moved sessionCreated and sessionModified to Client class
* Session cookie secret, close issue #89
* Warning: you need refactor code everywhere you use client.session
Merge pull request #112 from tshemsedinov/master

Changes from master branch