St3

[jlknuth]

This should fix two bugs under St3.

• The first is that after starting an EasyMotion with cmd-;, escape didn't bring you out of the motion. Some really crazy things were happening, liking repeated hits to esc acting like undo commands.
• The second is that if you hit return enough times to cycle through all your jump groups more then once, the EasyMotion didn't clean up after its self and so placeholders were left behind. This seemed to be related to the fact that each time a new jump group was highlighted, the old jump group's placeholders were left behind (at least this last part seems to happen under the master branch as well.)

[tednaleid]

awesome, thanks for the PR, this fixes #40