New features: 

- Added flag ``--all`` to show all the PRs
- Added auth flag ``--user`` to store the github's user name
- Moved filters into pulls
- Moved reviewers into pulls
- Renamed Maintainer to MaintainerManager

Closes #8


- Added the issues flag ``--votes`` that displays the number of issues's votes ``+1`` filtered by the number specified by the user
- Refactored some of the issues methods (passing pointers instead of the variable) 


Closes #51 
Closes #33