Python compatibility, custom formatting, improved debugging

• Remove the unreliable syntactic sugar [fix #2]
• Add a simple example of a BeakerLib test
• Improve the output, fix the encoding issue [#21]
• Add sources as value for string formatting
• Show source files in debug mode [fix #15]
• Allow deeper one-line hierarchy [fix #17]
• Update the list of supported Python versions
• Use name 'root' for directory where Tree is rooted
• Fix the full path custom format example
• Move documentation to the fmf rpm package
• Remove entry_points, custom format merged into fmf
• Add a few custom format examples
• Update docs with the custom format support
• Run both Python 2 and Python 3 tests locally
• Make eval() work with with Python 3 as well
• Integrate custom formatting into base & cli
• The first draft of output formatting
• Enable python3 tests, python3 executable in Fedora
• Python 3 compatibility changes
• Show nothing if there are no metadata [fix #12]
• Clean up before preparing the source files
• Make setup methods compatible with older pytest