Further integration with company-mode

- show type annotation (module/class/instance/function)
- C-w to view candidate definition during completion
- maintains ordering from jedi (now __methods__ are no longer on top)
Use HTTP/1.1

Also prevent isort from organizing imports before path has been initialized.
Process documentation in the server

This avoids asking the user for a choice when there are multiple definitions.
Add jumps and navigation of jedi definitions

This adds navigation methods goto_definitions, goto_assignments and
usages. Also traces jumps in a jump stack. Further described in #30.
Clean up tests

Tests were hard to read when the source and (line, col) were defined in
different locations. Now the source is inline and (line, col) is parsed
from the special cursor symbol `_|_`.
Remove fixtures and old tests