fix StaticHandler process http ranges header bug

[fznply]

support ranges as below:
Range: bytes=0-499
Range: bytes=-500
Range: bytes=500-

fix end_pos
Content-Range: bytes {start_pos}-{end_pos}/{total_length} // end_pos <= total_length -1

[danieldaeschle]

Maybe it is better to pull branch 0.1.0 and create a pull request to 0.1.0 instead of master. 0.1.0 contains black which formats your code.

[fznply]

i create a new pull request to 0.1.0 #143