[WIP] Release 0.3.0

This release includes 4 new features, 2 improvements and 3 fixes.
Please note that this release break the compatibility with Python 2.5: only Python 2.6 or 2.7 are supported yet.

The release notes can be read on our official documentation: http://docs.centralreport.net/unix-agent/releases/0.3.0

__All commits made since the version 0.2.0:__
https://github.com/CentralReport/CentralReport/compare/master...release-0.3.0

## New features
- [x] #58: CentOS distribution support
- [x] #67: Travis CI and silent installer/uninstaller
- [ ] #70: New online installer and uninstaller
- [ ] #82: New CLI Manager

## Major improvements
- [x] #72: Added a check for the webserver port availability
- [x] #74: Bash functions cleaned

## Fixes
- [x] #73: Removed old config.py script
- [x] #79: Removed support for Python 2.5 and older
- [x] #81: Removed flot.js library


# Todo before merging:
- [ ] Update the version number in the configuration
- [ ] Add the release date in the NEW file