get count in normal mode
add count to some commands
normalize count to 1
remove timeout
handle letter `0` in command
switch tab relative to current tab with count

- it wraps when count = 1, the same as the original behaviour
- it goes to the first or last tab when count exceeds boundary
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
refactoring switch tab commands
Merge branch 'master' into support-count-commands
support count when follow links
Merge branch 'support-count-commands' into local-dev

Conflicts:
	extension/packages/commands.coffee