Parallel builds

Added:

• md5 hashing of source files in gem as source_digest parameter
• COVERALLS_PARALLEL for merging parallel build support
• Tddium (Solano Labs) CI support
• license (@tagliala)
• COVERALLS_ENDPOINT for https://enterprise.coveralls.io support
• Appveyor CI support (@ianheggie)
• Coveralls::Output.no_color to disable colorization.

Fixed:

• SemaphoreApp sha details (@dontfidget)
• deprecations
• clear text repo token sometimes shown in logs (@amercier)

Full log: v0.7.0...v0.7.9