Fix #348: Make f always open links in the same tab

By temporarily removing `target="_blank"` from links when
simulating clicks on them.
Merge pull request #384 from zhuochun/issue-348-link-target

Make `f` always open links in the same tab
Fix #393, #380: Don’t suppress Esc in browser chrome
Fix #385: Support counts
Add count support to scrolling commands
Add count support to tab switching commands

- It wraps when count = 1, the same as the original behaviour.
- It goes to the first or last tab when count exceeds boundary.
Add count support to tab moving commands
Add count support to follow link commands
Add count support to tab closing/restoring commands

The current tab and count-1 tabs to the right are closed. If the current tab is
pinned, no tabs are closed at all.
Add count support to back/forward commands
Add count support to command_go_up_path
Merge pull request #385 from zhuochun/support-count-commands

Merged manually, in order to do everything requested in
<https://github.com/akhodakivskiy/VimFx/pull/385#issuecomment-57518289>.
Merge branch 'master' into develop
Merge branch 'develop' of github.com:akhodakivskiy/VimFx into develop