token: push grn_token_mode to grn_ctx for tokenizer
token: add tokenizer token skip
token: add tokenizer token skip with position
tokenizer: add token_mode in grn_tokenizer_query
token uvector: add token_mode pop
Merge pull request #193 from naoa/add-token-position-skip

push grn_token_mode to ctx and  add tokenizer token skip/skip with position for tokenizer

Patch by Naoya Murakami. Thanks!!!