Data Validation for club and player

Fixed validation errors and constructed basic unit tests for club and
player data models. Added the mongoose-unique-validator module to help
with data validation in mongoose.
Removed club model

Clubs become unnecessary and have been removed in a move towards a more
clearer data model pattern
Redo data models

Added the League model and redid the Team model. The new data model
follows the following pattern:
User: Ajax
League: Eredivisie
Team: Amsterdam
Players: Ricardo van Rhijn, Davy Klaasen

User: Ajax
League: Premier Soccer League
Team: Cape Town
Players: Sonwabile Cecil Lolo, Dominic Isaacs

Where each user can belong to multiple leagues with the same descendant
structure
Merge pull request #1 from toksfifo/update-unit-tests

Update unit tests