Misc improvements

[dwbruhn]

• improve parameter assertions
• include TypeScript/Flow typings to aid development
• set up Travis integration
• add Java compilation to Travis build

[dwbruhn]

• add compilation using Closure compiler API

[dwbruhn]

• support array of region codes in regionCode parameter
• support minimal validation via libphonenumber isPossibleNumber: https://github.com/googlei18n/libphonenumber#highlights-of-functionality