Fix bad return values in pool' handle_calls
Use byte_size/1 instead of length/1 on binary

By all means it seems that hackney_util:join return binary value so
length/1 is not applicable, byte_size/1 is.
Merge pull request #20 from keynslug/fix/pool_bad_returns

Fix bad return values in pool' handle_calls
Merge pull request #22 from keynslug/fix/binary_size

Use byte_size/1 instead of length/1 on binary
Provide a way to set connection timeout

... and set a reasonable default of 8 seconds.
Merge pull request #23 from keynslug/fix/conn_timeout

Provide a way to set connection timeout
make sure we return {error, term()}

Header fetching errors triggered a special case when it was about
matching an error. remoe it so we can consistantly handle errors.
fix parse_transform include
store the method
use field/1 to encode the multipart id
fix multipart
make sure we correctly handle chunked encoding when sending files
fix multipart encoding when sending a file
remove spurious logs
add support for partial file uploads

With this change you can now send only part of a file by setting from
where to start and the number of bytes to send. If the transport and the
OS support a zero-copy sent (using the sendfile API) will be used.
bump to 0.4.1
return received buffer when no content lenght is given (http 1.0)

- return the buffer and mark the response as done when the connection
  is closed when no content-lenght is given and the HTTP version is 1.0
- return the buffer on error closed in other cases:

    {error, {closed, Buffer}}

fix #21
fix indentation
add more doc for the new sendfile option
support partial file upload in multipart streams as well.