Remove bashisms in bin/clone

pushd/popd are not supported in all /bin/sh implementations, use the
more standard `cd -` to return to initial position. The `cd -` may
actually be completely unnecessary though, as long as the script
is executed rather than sourced the final directory change has no effect.
Add tests for two more handlebars features

* Test extended comments in the form of {{!-- --}}
* Test the @root property for accessing template root context
Tests for empty array and object in section and each

One of these tests, 006-simple-section-011.json, does not pass with
the current lightncandy.  This is because {"foo": {}, "bar": []} has
the same output with json_decode($json, true) for both foo and bar.

To resolve the issue lightncandy would at some point in the future
need to handle popo's in the input data.
Add tests for {{else}} in section and each context

One test, 036-sectionelse-005.json, fails due to a pre-existing
issue handlebars having different handling for [] and {} in
section context.
Merge pull request #2 from ebernhardson/section-empty-object

Tests for empty array and object in section and each
Merge pull request #3 from ebernhardson/root-and-comments

Add tests for two more handlebars features
Merge pull request #1 from ebernhardson/remove-bashism

Remove bashisms in bin/clone
Merge pull request #4 from ebernhardson/each-else

Add tests for {{else}} in section and each context
cd .. is more readable
Auto test on zordius/lightncandy@a826b8a1ab11cde4cc6dbaf8d4399ae595bf3f20
up
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Auto test on zordius/lightncandy@97b92c6d432ac45e19e29b2067d70decd8933626
add a testcase in test 036
add 8 known issues ( 036-sectionelse-005 and 006-simple-section-011 )
Merge branch 'master' of github.com:zordius/HandlebarsTest
Auto test on zordius/lightncandy@e142b6e116f63a82b3510fdaaf38dc9e3e476b57
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