Streaming-form-data

- Major performance improvements; we're now able to parse ~1800MB per second,
from ~15MB per second in the previous version (thanks [kolomenkin])

- Fix parser bug which could lead to spurious CR or CRLF being added to the end
of transferred form field value (thanks [kolomenkin])

- Make `filename` (from the `Content-Disposition` header) available as
`self.multipart_filename` attribute in `Target` classes (thanks [kolomenkin])
- Add example usage for `bottle` framework (thanks [kolomenkin])
- Refactor tests to work with random bytes instead of increasing repository size
with test files (thanks [kolomenkin])
- Make `Content-Type` header lookups truly case-insensitive (mixed cases also
allowed) (thanks [kolomenkin])

- Make `Content-Type` header lookups case-insensitive

- Performance: mark `active`, `found`, and `inactive`
properties on `Finder` instances as `cpdef`-ed methods, decreasing
the Python-space operations for an increase in speed
- Performance: remove `_Failed` exception and replace it with error codes,
decreasing the Python-space operations for a speed increase
- Include `Cython`-generated annotation file to keep an eye on the
Python-interaction level

- Performance: `cdef` declare `long` variable responsible for
iterating over the buffer