add pending pre_processor tests

basically we're going for almost-parity with i18nliner(.rb)

inspiration here: https://github.com/jenseng/i18nliner/blob/master/spec/pre_processors/erb_pre_processor_spec.rb
rudimentary preprocessing
yay recursion
disallow block expressions calls inside t-blocks

yo dawg
preliminary wrapper support

just pure html wrappers atm, no expressions
jshint
reuse identical wrappers
add unescaping test
concatenate expressions in wrappers
generate placeholders for expressions
placeholders (and wrapper concatenation) for helpers
nested t-block support
generate placeholders for empty markup
extractor goodness, add i18nliner(-js)

simplify extractor to only deal with inline t calls, since the pre-
processor converts block t calls for us. add i18nliner(-js) so we can
leverage things like CallHelpers, TranslateCall, etc.

remove I18nKeyStore, since it was basically ported over into i18nliner, so
it became redundant.
update readme
Merge pull request #1 from jenseng/preprocessor

Pre-processor, basic i18nliner.js tie-in