[all] Release v0.3.0

[demurgos]

• [Breaking change] Update to swf-tree@0.4.x
• [Feature] Implement parsers for the following tags: DoAbc, ScriptLimits, SoundBlock, SoundHead, SoundHead2, StartSound, StartSound2, SymbolClass
• [Fix] Drop JpegTables signature check
• [Fix] Update dependencies
• [Fix] [rs] Synchronize implementation with Typescript
• [Fix] [rs] Use pure-Rust libraries for decompression. Thanks @eddyb
• [Fix] [rs] Accept key code 8 in button cond
• [Fix] [rs] Keep opaque length in x-ajpeg image data
• [Fix] [rs] Update to Rust 2018
• [Internal] Add Travis CI integration
• [Internal] Update README.md