PHP version upgrade

Upgrade php version to ^7.1
Upgrade phpunit version to ^7

0.4.1

Move Monetary::$currency_templates to static property so serializatio…

0.4.0

Allow negative templates for currency formatting

0.3.2: Introduce Cache_None for unit tests

Cache_None is used in Source_RemoteTest.
When the functionality of caching should is not the essential thing
being tested in a unit test it should not be used.

Also it allows the Source_RemoteTest::test_serialize test to be run
multiple times on the same system without failing.

0.3.1

Moved the serialization implementation up in the chain of sources

Sourceable::rate instead of Sourceable::exchange_rates

0.3.0

Added Source::rate method instead. Tests and formatting.

0.2.2

Source is Serializable and Source_Static accepts arrays

Allow setting default currency and precision

0.2.1

Fixed code in usage example

Requestable interface, full test coverage

Added Remoteable and CURL driver for Source_Remote

• Added Remoteable interface
  • It is used in Source_Remote similar to Cacheable
  • It could be set via the constructor.
  • It could be get or set via the request_driver method.
  • When making a request $this->request_driver()->request() is used.
• Added CURL class implementing the Remoteable interface
  • It is the default request driver for Source_Remote.
• Other improvements like more static:: usage.

100% test coverage

More test coverage and better extensibility

0.1.1

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