0.5.1 - IRT ready

• support {free: true} in #export DBSolve
• update _Component.clone() method to exclude cloning of namespace
• fixes to sbmlParse() function for clear math expressions
• "src/browser.js" is an entry point for browser apps and webpack
• methods references() to _Component
• add "omit" property to #export formats: JSON, YAML, XLSX
• exclude "fs" and "path" libs from core code for browser support
• updates to nunjucks templates for easy usage in browser apps
• remove specific JS errors from Container and components
• multiple dependencies updates