Falco 2.0 Release

- Added 2 new analysis modes - Alignment-only and Transcript Assembly
- Added Python3 support to all analysis modes (including Quantification analysis mode) and made PySpark use Python3 by default
- Added support for using custom AMI when launching EMR cluster (require EMR release >= 5.7)

- Updated README with links to customising Falco page

Initial commit of Falco