(MCO-215) Move exception classes from mcollective.rb to lib/mcollective/exceptions.rb
The exception classes are apparently a bit difficult to find where they are now located.
This commit creates a file called exceptions.rb, and moves the exception classes there.
(MCO-188) Update rubygems dependency to 1.3.7 or greater

Mcollective will fail to start if certain very old versions of rubygems are
employed. Those versions happen to be readily available on el5. Fortunately,
yum.puppetlabs.com offers version 1.3.7 of rubygems, which alleviates this
problem. This commit updates the requires for rubygems to specify a minimum
version of 1.3.7, to ensure that once installed mcollective will actually be
able to start.
Merge pull request #174 from MichelleJaeg/improvement/master/exceptions.rb

MCO-215
Merge pull request #175 from haus/ticket/master/mco_188_update_rubygems_requires

(MCO-188) Update rubygems dependency to 1.3.7 or greater