avoid extraneous first-time expression eval

R=arv
BUG=

Review URL: https://codereview.appspot.com/73050044
Fix tests to not use Node.unbind

R=arv
BUG=

Review URL: https://codereview.appspot.com/75910046
Update README.md
Fix tests cleanup in IE
fix licensing
Add tests for true, false and null literals expressions
If the path is true, false or null don't treat that as simple path

This is so that `{{ true }}` is treated as true and not as `model.true`.

Fixes #24
Merge pull request #25 from arv/true-in-expression

True in expression
Add tests with numeric literals
Treat numbers as numbers in expressions

This is so that `{{ 1 }} ` is treated as `1` and not as `model.1`.
Same goes for `{{ 1.2 }}` which should not be treated as `model.1.2`.

Fixes #24
Merge pull request #26 from arv/numeric-litarals-in-expressions

Numeric litarals in expressions
Revert "Treat numbers as numbers in expressions"

This reverts commit 3978609509b8b2399c0561ba899eb9807c6cb465.
Revert "Add tests with numeric literals"

This reverts commit 16291cd5f99d3b78c31fca3ef668c266c5b5c422.
Treat numbers as numbers in expressions

This is is revert of the following two reverts
41155259edd18ef56a88d9b05370292bb9c79a38
d03bd9b68a0a0cff068eac28dbd7292e9ab5774f

The original commit had an issue where '' was treated as 0.
Merge pull request #27 from arv/expression-literals-again

Treat numbers as numbers in expressions
initial fancy expressions
fixes