nonassign $compile error message is vague

[wesleycho]

Oftentimes the error message thrown by

angular.js/src/ng/compile.js

Lines 3122 to 3124 in d98c5f0

	throw $compileMinErr('nonassign',
	"Expression '{0}' used with directive '{1}' is non-assignable!",
	attrs[attrName], directive.name);

is vague, and is hard to determine exactly what is wrong.

For example, the error message I am seeing is Error: [$compile:nonassign] http://errors.angularjs.org/1.4.9/$compile/nonassign?p0=undefined&p1=foo, which does not tell me the attribute name.

Tweaking the text on this to output the attribute name could be a huge boon, and a minimal addition - I can open a PR for this if desired.