tabr 0.3.5 release

• Added alternate input specification for sf_phrase. Instead of providing the first three function arguments, string, fret and info, separately, you can now provide everything to the first input string as a single character string containing all three components separated by semicolons. This makes it easier to reason about the input by time step rather than by argument.
• Added chord helpers: chord_root, chord_top, chord_slice, chord_is_major, chord_is_minor.
• Added notation-frequency conversion helpers: pitch_freq, freq_pitch and other related functions.
• Added several more functions for inspecting and manipulating noteworthy strings.
• Code and documentation formatting and style overhaul based on stricter linting rules.
• Updated documentation and unit tests.