Chain cache implementation

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branch : feature/stackable-cache
APC, Memcahe and XCache adapters

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branch : feature/stackable-cache
Remove coverage-html generation in tests

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branch : feature/stackable-cache
Rename XCacheAdapter to XcacheAdapter

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branch : feature/stackable-cache
rename : src/SibSet/Cache/Adapter/XCacheAdapter.php => src/SibSet/Cache/Adapter/XcacheAdapter.php
Added tag 1.2.0 for changeset 4237e3835bdb

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branch : feature/stackable-cache
Upgrade extension check

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branch : feature/stackable-cache
Remove development phpunit.xml

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branch : feature/stackable-cache
Add readme and license

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branch : feature/stackable-cache
Add cross vcs ignore

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branch : feature/stackable-cache
Merge branches