Allow teamcity to track coverage for builds

We'll still use coveralls.io, though! This
just makes it so that TeamCity is aware of
change of code coverage when viewing build
results.
Fix TeamCity Service Message quoting
Fix awk: redirect in coverage_file
Fix quoting of TeamCity Service Message
Fix TeamCity Service Messages, 'key', not '<key>'
Merge pull request #151 from pexpect/teamcity-coverage-support

Teamcity coverage support