clipr 0.6.0

Thank you to @wangyuchen for making the following suggestions:

• To make clipr more pipe-friendly, write_clip() now defaults to return_new = FALSE, and will instead return the initial object that was passed in. To get the old behavior, pass return_new = TRUE

• In an effort to make write_clip() and read_clip_tbl() more symmetrical, write_clip() now defaults to writing out row and column names when they exist.

• Introduces write_last_clip(), a wrapper function for write_clip(.Last.value)