spec: fix failing test case for cancel behavior
fix cancel behavior

ref: #34
spec: add more test cases for cancel behavior
Fix cancel behavior for stay command
spec: improve test case to see error position
fix not to change search patterns for Vim which doesn't have keeppattern
fix s:execute_search to work with keeppattern for lower vim version
fix not to reset v:searchforward
Merge branch 'fix-cancel-behavior'
lint: ignore v:searchforward