Moved MongoLid::__construct method to beginning of the file

- Changed it to be more readable
Removed unnecessary 'else' statements

Removed all 'else' statements followed by a 'return'. This
cases does not make clear what the normal path of execution
is.
This pattern is called 'Guard Clauses'
(http://www.refactoring.com/catalog/replaceNestedConditionalWithGuardClauses.html)
Changed code style in order to fit PSR standards
Exchanged validation conditions of MongoLid::save method

Changed order of '$force' and 'isValid()' conditions
in order to avoid unnecessary execution of validation
when '$force' is true
Merge pull request #65 from rplansky/code-style-and-logical-refactors

Code style to fit PSR and removed some unnecessary 'else' statements