Fix "\\{{" immediately following "\{{"

Escaped-escape mustaches ("\\{{") immediately following escaped
mustaches ("\{{") were being handled incorrectly.

Fix the lookahead to make sure yytext still contains the appropriate
slashes when we pop out of <emu> so they can be handled consistently
by the initial state.
Update base.js

Give users the index for properties. When I am rendering a radio button I use key-value pairs, but I can't use either as unique identifiers because they likely contain invalid identifier characters. I added "first" as an index as well, but have no particular use case for first. Since there is no way to detect "last", I didn't add that property.
Merge branch 'patch-1' of github.com:cgp/handlebars.js into cgp-patch-1
Use strict comparison for first
Add tests for object @index and @first handling
Relax packager dependency
Use charAt rather than string index

Older versions of IE do not support [] access to string contents so charAt must be used.

Fixes #677
Use shouldThrow helper for test asserts
Move away from should asserts to internal

This is needed as neither Sinon nor Chai support in-browser testing under IE.
Fix tokenizer tests under IE
Concat tests together for inbrowser exec
Add sauce labs testing support
Add selenium badge
(Attempt to) Limit sauce tests to one travis build
Create matrix target for 0.10 only
Optimize travis build with publish option
Add travis build caching
Hide success messages when running in sauce

This should help debug the firefox issues that only occur when executing against sauce.
Skip leak check under FF
Merge pull request #681 from wycats/sauce-tests

Adds in-browser testing and Saucelabs CI