Merge branch 'release/0.6.1' into develop
Clear briefing highlight rect when not applicable.

Failing to do so caused Issue 126, where after transitioning from a
briefing point with a highlight rect to one without, the highlight rect
would continue to be visible.
Merge branch 'briefing' into develop
Don't cache TextDriver lines between frames.
Don't keep references to reallocated slices.

Caused unnecessarily-duplicated entries in text screenshots.
Extract UTF8 text and JSON.
Merge branch 'text-driver' into develop
Merge branch 'utf8' into develop
Integrate ext/*.

Integrate ext/gmock-waf 0eec1f8.
Integrate ext/libpng-waf ed8470c.
Integrate ext/libsfz 79d8f33.
Integrate ext/libzipxx 8f6c541.
Integrate ext/rezin af3b2b7.
Default to clang.

Fix a host of compiler warnings introduced in the switch.
Merge branch 'integrate' into develop
Compile with --std=c++11.

Integrate ext/gmock-waf b391e0d.
Integrate ext/libpng-waf 85f6656.
Integrate ext/libsfz b558d31.
Integrate ext/libzipxx c8122e1.
Integrate ext/rezin eec2ee7.
Swap SFZ_FOREACH for range-based for.
Swap sfz::scoped_ptr<> for std::unique_ptr<>.
Swap sfz::linked_ptr<> for std::shared_ptr<>.
Merge branch 'cxx11' into develop
Integrate ext/{libsfz,libzipxx,rezin}.

Integrate ext/libsfz da3b4ea.
Integrate ext/libzipxx 0a7b2bc.
Integrate ext/rezin 6ea8e24.
Merge branch 'integrate' into develop
Emplace into lists of strings.
Return unique_ptr<> objects.