[Issue #63] Add error handling for the timer error (needs further investigation.)
Added `sp-cheat-sheet` to generate SP function overview. Examples in docstrings annotated with ZERO WIDTH SPACE for fontification.
Added prefix argument to `sp-cheat-sheet` to only show examples if possible. Added examples to docstrings, univied the docs format.
Automatically use fallback command if the buffer is read-only (e.g. debugging, dired, special buffers etc.)
Enhanced `sp-beginning-of-sexp` and `sp-end-of-sexp`, swapped their default "sp" binding.