Added new exchanges and build instructions to README.
Exchange implements Serializable.
Added test to test serialization.
Added a new field to exchange to hold the name of the exchange given by his subclasses.
Removed the default constructor from subtypes of Exchange and the constructor from Exchange which received only a string.
Added a static method to Exchange to return all subtypes of Exchange and test cases to exercise this functionallity.
Merge branch 'master' of github.com:andrefbsantos/libdynticker
Removed Serializable from Exchange, we will never need to serialize
them.
Corrected links in README.