added `dash-at-point-with-docset` defun to choose a docset with completion-read and then search for the word at point
Merge pull request #6 from waymondo/master

`dash-at-point-with-docset` for choosing a docset from completion read
Support various major-modes
Merge pull request #7 from yasuyk/support-various-major-modes

Support various major-modes