Travis support
Fixing SS 3.1 support. Changing minimum requirement to 3.1 as a result.
Merge pull request #20 from halkyon/3.1-fixes

Fixing SS 3.1 support. Changing minimum requirement to 3.1.
Use the correct class name instead of $databaseConfig['type']
FIX Throw error if trying to add a table-less DataObject class to index

Its impossible for SearchUpdater#handle_manipulation to figure out the difference
between writing to a table-less class (like Page if theres no $db set) and the
table-having parent (like SiteTree) because it only examines the DB manipulation

This meant if you tried to index Page without setting $db fields, only subclasses
that did have $db fields would be indexed

We cant fix, but we can throw an error if you try to do that
Merge pull request #21 from silverstripe-rebelalliance/fix/not_indexing_tableless_classes

FIX Throw error if trying to add a table-less DataObject class to index
Fixed composer constraints
Note about installing 'text extraction' feature
BUG Remove non-displayable chars from Solr highlight results
Adding Phockito dependency
No longer test against 3.0
Add subsites and cms modules to dev requirements (for tests)
Cross-reference textextraction module in docs
NEW Shared index fields
Fixed tests (wrong var names)