Add gitattributes to exlude files from packaging (closes #548)

The "master" branch is now dedicated to solarium 4.x.
A new "3.x" branch was introduced to still maintain solarium 3.x (previously in master) with minimal bugfixes and security updates for some time, especially for people using older PHP or Solr versions.

* all components shpould be re-usable for custom query types and not be restricted for "select"

* cleaned-up QueryType\Select tests

* cleaned-up traits and introduced first interfaces to treat some components and query types indentically

* added a terms component

* fixed typos

Add a pagination example, see #521

The 3.x Suggester was in fact Spellcheck. the 4.x Suggester is a real Suggester now.

* run solr on travis

* use java 9

* fixed matrix

* added a first intergration test that select a result from the Solr techproducts example server

* added comment and dummy assertion to testPing()

Cleaned up suggester query and added missing parameters

Fixes bugs from PR 484; fix Http adapter for extraction requests

Make suggester query use suggest prefix