add exchange rate functions
Merge pull request #46 from otaviojava/exchange_rate_provider

add exchange rate functions,  fixed problem of exchange rate when are the same currency unit.
Added minimal travis CI config.
Fixed build issues.
Merge branch 'master' of https://github.com/JavaMoney/jsr354-ri
Added JDK entry.
Added coveralls config.
Updated readme config, integrated with CI.
Updated coverage setup.
Updated coverage setup.
Added jacoco config.
Replaced  printStackTrace() with JUL statement.
Replaced printStackTrace with exception.
Removed commented code.
Minor quality fixes.
Fixed logger usage.