Snowplow JavaScript Tracker v0.13.0

New functionality (custom contexts, transaction currencies, setPlatform) and some general tidy-up.

• Release blog post
• Custom contexts guide

New functionality

1. Added custom unstructured contexts (#49)
2. Added currency field to ecommerce transactions (#34)
3. Added setPlatform support, thanks @rcs! (#25)

Small additions

• Added base64decode to Tracker (#36)
• Added null check to requestStringBuilder() (#40)
• Added array helpers (#41)
• Fixed (harmless) bug in base64.js (#35)

Project tidy-up

• Added fully retrospective CHANGELOG (#20)
• Switched to Semantic versioning & only put MAJOR version in hosted path to snowplow.js (#47)
• Added package.json (#38)
• Added retrospective tags back in (#22)
• Restructured folders (#21)
• Update .gitignore to be node-friendly .gitignore (#52)