Remove pragmas, rely on identifier instead

[phpnode]

It's fragile and precarious to rely on a particular identifier name for this kind of thing. It's too easy to call an identifier markdown some time in the future and find yourself fighting a bug that seems totally impossible. This PR scraps the idea of pragmas and relies on the name of the identifier being imported or required instead.

[threepointone]

This is great! I'll remove the bit with self linking and use a webpack resolve alias instead. Thanks much!

[threepointone]

merged and published in 1.1.3. Thank you very much!

[phpnode]

Cool, it's worth noting that this is not totally foolproof, the following should work:

var foo = require('markdown-in-js') // ok
var bar;
bar = require('markdown-in-js') // ok

the following will cause pain

var foo = require('markdown-in-js') // ok
function demo () {
  var foo = 123
  console.log(foo) // boom because we don't know that foo is shadowed.
}

and

var foo = require('markdown-in-js') // ok
foo = 123
console.log(foo) // oh dear, we don't know that foo has been reassigned

It's not hard to fix this issue but it's worth adding a note in the README in the meantime

[threepointone]

yes, it's also why I went with a simple hardcoded value in the first place, just needed something that worked. I'll also make the error more meaningful in the above cases.