Fix README: bashrc -> zshrc
Merge pull request #47 from ehamberg/patch-1

Fix README: bashrc -> zshrc
Modified some conditional expressions (with DeMorgan's Law) to fix syntax errors on some shells
Merge pull request #48 from feltnerm/DeMorgan_on_conditions

Exclamation mark after `if` statements are causing a syntax error on some zsh
versions (think 5.x). Also, fix `antigen-revert` not returning when revert file
is not present.
handle (ignore!) blank lines in antigen-bundles
Defer `compdef` calls until after `compinit -i` is called
process deferred compdefs in the order they were called