Performance fix: avoid redundant analyses.

Flake8 is relatively fast, but do_update_state is called many time
at each load and save, making the whole thing slow.
(1 second to save on a SSD-powered laptop?!)

According to the docstring, the method is only there to start one analysis
on load. The 'loaded' signal does a better job at this (it is only triggered
once per call) and works the same as 'saved'.

Loading and saving (on my machine) is still noticably slower than without
the plugin, but it is now much better than before.
Run analyses asynchronously.

Even if flake8 is kinda slow, it doesn’t block the UI anymore.
Merge pull request #1 from SimonSapin/fix-redundant-calls

Performance fix: avoid redundant analyses.
Remove double declaration of class ResultPanel
Catch attribute errors when none language is defined in a gedit document
Remove unnecessary import os
Merge pull request #2 from SimonSapin/fix-redundant-calls
	Run analyses asynchronously.
	Even if flake8 is kinda slow, it doesn’t block the UI anymore.
Remove typo error in creator email
Display errors of current line in statusbar after saving if current line have
  an error/warning, Fix errors due to threading
Display errors of current line in statusbar after saving if current line have
  an error/warning, Fix errors due to threading
Fix panel not displaying right documents error on tab changed
Copy not local file (sftp for example) on /tmp so flake8 can analyse them
Fix attribute error when get_language return None
fix url of website
fix url of website, and fix remove tag even if location not found
Merge branch 'master' of https://github.com/khertan/gedit_flake8