doc: clarify description of assert.ifError()
doc: clarify description of assert.ifError()

This fixes a few typographical errors (comma splices and the like) and
clarifies the description of assert.ifError(). It also standardizes the
document on "inequality" rather than having both "inequality" and "non-
equality".

PR-URL: https://github.com/nodejs/node/pull/2941
Reviewed-By: Michaël Zasso <dc852f7f42c586356f6be32b8780273088b3bded@gmail.com>
Reviewed-By: Sakthipriyan Vairamani <b84950071fc99921a72f4fa56f6cad2496b3223c@gmail.com>

dreamllq/node,dreamllq/node,dreamllq/node,dreamllq/node,dreamllq/node,dreamllq/node,dreamllq/node,dreamllq/node,dreamllq/node