UI (big files): add indication of big file

- add indication to gist in the list that has a file larger that 1mb
STYLE (css): small css fixes

- small CSS fixes
- default avatar (github default avatar) size fix
FIX (single gist): Loading gists no longer occasionally enable edit mode.

Gists original data now contain big files for reverting changes.
Merge remote-tracking branch 'origin/master'

* origin/master:
  STYLE (css): small css fixes
  UI (big files): add indication of big file
  STYLE (css): fix css colors and glitches
  FIX (loading files over 1mb): Add load file button on truncated content, changed editor to be self contained.
FIX (markdown links): All markdown links now open in a new browser window instead of inside the application.

Fixes #88
IMPROVE (markdown links): Remove unused injected services.
RELEASE: version 0.2.5b

- FEATURE (settings): add export/import of user settings
- FEATURE (settings): add export/import of user settings
- FEATURE (single gist): show fork info if gist is forked
- FEATURE (share gist): add auto-completion to share gist
- FEATURE (editor): add preview of markdown
- UI (big files): add indication of big file
- UI (css): add markdown css
- UI (css): update text fields to reflect valid/invalid state
- FIX (editor): fix font size settings issue
- FIX (dotfiles in gist): fix links of dotfiles
- FIX (gist API): gisto fail to handle files >1MB
- FIX (deleting a file): local copies of files now properly delete when not yet saved to GitHub
- FIX (drag & drop): drag area disappears on drag cancel
- FIX: Files that do not exist in github do not send a patch request upon deletion.
- FIX: Fix not being able to save when there is an empty file in create screen.
- FIX (single gist): notify upon Error when creating gist + validate filename with regex.
- FIX (single gist): URLs of gist API for single gist view.
- FIX (single gist): #81 where username was incorrectly pulled from json causing gist file url appear with no username parameter thus double slash.
FIX (create gist): Fix text overflowing from the description field

When text was too long in the description field the text overflowed over the entire application.
FEATURE (editor): add vim mode

- add vim mode to editor (enable from settings)

Closes #95
FIX (single gist): wrong direct link for uppercase characters in filename or extension

- fix wrong direct link for uppercase characters in filename or extension

Closes #93