Fixing the handling of (unmatched) optional capture groups (#75)

* adding test showing the problematic handling of optional capture groups

* do not return "null"-String

when an optional capture group is actually not matched

* upgrading travis jdk version

since it no longer supports jdk's older than 9:

> $ ~/bin/install-jdk.sh --target "/home/travis/oraclejdk8" --workspace "/home/travis/.cache/install-jdk" --feature "8" --license "BCL"
> Ignoring license option: BCL -- using GPLv2+CE by default
> install-jdk.sh 2020-06-02
> Expected feature release number in range of 9 to 16, but got: 8

* we no longer return the "null" string literal

* reduce assertions

Co-authored-by: Kirill Merkushev <lanwen@yandex.ru>

* Update .travis.yml

Co-authored-by: Kirill Merkushev <lanwen@yandex.ru>

Add word boundary (Fixed #68) (#71)

Add named-capturing group (#70)

* Add named-capturing group

* Update coveralls-maven-plugin version

* Add usage example for Builder#capture(String) and getText(String, String)

* Fix local variable name to camelCase

* Use assertThat instead of assertEquals

release with travis

release with travis

[maven-release-plugin] copy for tag v1.4

[maven-release-plugin] copy for tag v1.3

[maven-release-plugin] copy for tag v1.2

[maven-release-plugin] copy for tag v1.1

[maven-release-plugin] prepare release java-verbal-expressions-1.0