Add Travis CI support

[dexX7]

• Builds Master Core on Travis CI (Ubuntu 12.04 LTS)
• Tests daemon (./src/test/test_bitcoin)
• Tests QT (./src/qt/test/test_bitcoin-qt)
• Runs Bitcoin Core RPC regtests (https://github.com/TheBlueMatt/test-scripts)
• Runs Master Core RPC regtests (https://github.com/dexX7/mastercore-rpc-tests)

[dexX7]

A project maintainer (@m21) should head over to https://travis-ci.org/ and "sign in with GitHub" to authorize Travis CI.

Once synced, mastercore should be enabled:

I furthermore suggest to build only, if .travis.yml is present. This can be enabled in the settings of the repo:

Travis CI has a nice GitHub integration and reports the build success, which looks like this:

I'm not sure, if pending PRs are tested right after enabling Travis, but it can be forced to do so in the "pull requests" tab:

The result (which is actually based on this PR) looks like this: https://travis-ci.org/dexX7/mastercore/builds/45808383