Persist Dictionary changes in batches

We're seeing a segfault in production that happens to involve trying to
update about 50K columns in a row at once. No guarantees this will help,
but it generally seems like a good idea to batch these writes when
they're that huge.
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use parameters for pooling
spec to verify connection_pool functionality
Merge pull request #9 from ping4/connection_pool_fixes

Connection pool fixes
Add link to cequel-migrations-rails to README
add homepage link so rubygems users can easily get to github
Merge pull request #15 from ping4/gemfile_link

add homepage link so rubygems users can easily get to github
debugger not ruby-debug !
Clear out Dictionary @row on save unless loaded

Otherwise causes bad behavior in #slice method
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Calling ::load on a loaded Dictionary is a no-op

Previously it was clearing out the row but not re-loading data, making
the dictionary appear empty.
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Ability to change default consistency within a block
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Add link to cequel-migrations-rails to README