Team model

Will allow to users create their teams with bunch of cool stuff.
ability for manage Teams
create team feature
Quick sign in integration specs
deny to create more than one team
Add styles and traslations to create team inteface

Add styles, translation to create team form
Add javascript to convert team name into slug
Fix the bug caused 404 on failed team validation
Using friendlyId for teams
Refactor feature specs

Rename `quick_login` method into `sign_in_as` for better readability
Manage team

Add possibility to edit team data by team's leader.
Add possibility to disband team by team's leader.
Logo and description for teams

Add possibility to upload team's logo
Add possibility to fill in information about team
Teams list

Users now can view list of the teams and navigate to teams' pages from
that list
Invite members feature

Leader be able to invite members from members page
Deny access to manage team members for non leaders

Only leader can manage team's members
Fix bug displaying all invitees on each team
Fix styles for invite member form
Invites list page

  - Invited users can accept and/or reject invites from Invites page.
  - But leaders cannot accept invites from different teams until disband
    current team or choose another leader.
  - Fix bug where leader has ability to invite himself into the team.
  - Display validation message for already invited user
Display members' list on the team's page
Fix ability to visit invites page as guest