Peptacular

- removed labile mod check from pt.contains_sequence_ambiguity()

Added:
- condense_mods function to condense_to_mass_mods.py
- [potentially breaking] updated digestion and span functions to return generator objects
- added sequential_digest, digest_from_config and EnzymeConfig to digest.py
- regex strings which don't have the same start/end site will give a warning such as ([KR])
- fixed regex bug with nterm enzymes
- simplified supported enzyme regexes
- added simple fasta_parser since I kept recreating it in other projects, works with several input types
- some more tests
- added condense_to_mass_mods to mass_calc.py which condenses modifications to a single +/- mass value
- Fixed Docs
- Linting

Added:
- Full ProForma2.0 support
- proforma.py for handling ProForma strings (full support for ProForma2.0)
- Support for all types of internal fragment ions (ax, ay, bx, bx...)
- isotope.py for generating isotope distributions
- apply_static_mod and apply_variable_mods now support n/c term mods
- gno, resid, and xlmod support
- randomizer.py for generating random proforma sequences
- added mods module to handle loading obo files and finding mods
- added fragmenter to fragment.py

Changed:
- Terminal modifications notation has been changed to use []- and -[] for N- and C-terminal modifications, respectively
- All internal modifications now use [] notation
- Element masses/isotopes are generated using physics.nist.gov db
- Move static/var mod builders to mod_builder.py
- Moved combinatorics funcs to combinatorics.py
- All public functions are accessible from peptacular base (suggest using import peptacular as pt)
- Most functions now support a ProFormaAnnotation object
- Improved digest and fragment performance
- Improved docs

Added:
- Permutation / Combination / Product functions in sequence.py
- Immonium Ion support to fragment.py

Added:
- Added support for custom aa masses to mass.py and fragment.py

Added:
- Added isotopes and loss to fragment.py