[strings] add jsPerf and discussion about long strings with concatenation. Fixes #40
[arrays] use Array#slice to copy an array. Fixes #41
[hoisting] fix typo
[in the wild] add national geographic and gooddata
[arrays] believe in push.
[functions] add source about func declarations & blocks in different browsers
[functions] fix link to ecma-262 note
Fixed typo
Merge pull request #43 from mitsuruog/master

[functions] Fixed typo
[in the wild] add GoCardless and Razorfish
[performance] add article on layout and web performance
Fixed typo
[in the wild] add ExactTarget
Fixed typo
Merge pull request #46 from mitsuruog/master

Fixed some typos.
Merge pull request #45 from adamalex/master

[in the wild] add ExactTarget
translate into Japanese
Merge pull request #47 from mitsuruog/master

Translate into Japanese
[translations] update wording
[Translations] added german