Checking if we're currently within an escape sequence every single
loop iteration is wasteful.

This avoids an unnecessary alloc in the common case of strings
under 1024 chars.

`bytes` on PY2 are really `str`s, so `val[n]` returns a character
rather than an integer. Wrapping bytes values on PY2 helps us
preserve semantics without requiring branching on Python version
or version-specific lambdas to peek from `self._buffer`.

Shaves 100ms off my testcase's runtime.

Allow users to simply `from llsd import LLSDBinaryParser`

Re-export parse/format classes from main module

Speed up parsing notation LLSD