Clean up composer configuration

[acoburn]

Add scripts section with test and check scripts.
Remove redundant travis configuration
Add phpcpd to the -dev dependencies

See similar PR at: Islandora/Crayfish#25

What does this Pull Request do?

This does not change any code. It only changes the Composer and Travis-CI configurations, making it easier to test code. This also removes some redundant configuration in .travis.yml.

What's new?

There are two noteworthy changes to composer.json beyond the addition of the test and check scripts, namely the addition of a -dev dependency on phpcpd (which travis is expecting anyway) and it aligns the versions of phpunit and php_codesniffer to the versions defined in the Crayfish* repositories.

How should this be tested?

In the root of this repository, run composer test.

Additional Notes:

See here for more information: https://getcomposer.org/doc/articles/scripts.md#writing-custom-commands

Interested parties

@Islandora-CLAW/committers

[codecov]

Codecov Report

Merging #68 into master will not change coverage.
The diff coverage is n/a.

@@            Coverage Diff            @@
##             master      #68   +/-   ##
=========================================
  Coverage     93.63%   93.63%           
- Complexity        0       24   +24     
=========================================
  Files             3        3           
  Lines           110      110           
=========================================
  Hits            103      103           
  Misses            7        7

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