use for Go 1.8 "context" standard package, not "golang.org/x/net/cont…

[bstarynk]

Go 1.8 (& probably Go 1.7) has a standard internal "context" package which should be imported (in file sqlite3.go in place of "golang.org/x/net/context" external package.

[coveralls]

Coverage increased (+1.2%) to 63.858% when pulling 06cec77 on bstarynk:master into b2e4645 on mattn:master.

[coveralls]

Coverage increased (+1.2%) to 63.858% when pulling 06cec77 on bstarynk:master into b2e4645 on mattn:master.

[coveralls]

Coverage increased (+1.2%) to 63.858% when pulling 06cec77 on bstarynk:master into b2e4645 on mattn:master.

[mattn]

This break go1.6 .

[bestplay]

I use this go tool fix -force context to upgrading the import path of the Context package.