Whippet v0.3

[timbitz]

This would merge the current state of Whippet v0.3. Changes include:

• [x] Support for Bio v0.2/0.3 (including static-qual support)
• [x] Tests in test/runtests.jl #3
• [x] Documentation of output types #3
• [x] GTF support #3
• [x] Greater efficiency of SGAlignment data storage, and annotation types/storage #16
• [x] Splicing complexity in entropy #24
• [x] SAM format output support for repetitive alignments #14
• [x] Psi output bugfixes #2
• [x] Alignment scoring in percent identity #21