Add try it buttoms to all examples

[labra]

We added try it buttoms to the first examples in ShEx chapter. Add these buttoms to the rest of the examples in the book.

We created a latex command \tryit{...} which is blank for plain LaTeX and is defined for Hevea. One problem is that LaTex doesn't seem to like long URLs with %, so we use the https://goo.gl/ service to shorten the permalink generated by shaclex.

However, goo.gl also seems to dislike the long url generated by SHACL examples. At this moment, we still need to add more ShEx examples (it is just a matter of adding them) and search for a solution for the SHACL ones.