FIX: PostgreSQL deadlock sqlstate

In PostgreSQL, when the deadlock error occurs, Sequel::DatabaseError is
raised instead of Sequel::SerializationFailure.
Because the sqlstate of deadlock is '40P01' in PostgreSQL. It is not '40001'.
Fix spelling error
Update CHANGELOG
Merge branch 'patch-1' of https://github.com/tmaier/sequel
Add support for conditions on triggers in postgres
Avoid false positive cache hits when using STI.
Minor cleanups for PostgreSQL create_trigger :when option

Add method documentation for it, and simplify the handling.  Also,
only test the behavior if the PostgreSQL version being tested
supports it.
Merge branch 'master' of https://github.com/pete/sequel
Fix specs to run on ruby 1.8, update CHANGELOG
Fix regression in class_table_inheritance plugin when lazily loading column in middle table

This regression happened when you have a hierarchy such as:

 class A < Sequel::Model; plugin :class_table_inheritance; end
 class B < A; end
 class C < B; end

And you retrieve a partially loaded instance of the subclass
via the parent class:

  c = C.create
  c = A[c.id]

If you try to call a column method for a column contained in B's
table:

  c.column_in_table_b

You would get an error because it qualified the column with C's
table instead of B's table.

To fix this, options need to be added to lazy attributes getter
method creator so that you can define the dataset and qualifier
to use inside the getter.

class_table_inheritance can then use the options to setup the
lazy attributes getter properly.
Document passing a Hash parameter to on_duplicate_key_update
. "with with" -> "with"
Add search_path documentation for postgresql driver options
Add some more detail to the search_path documentation
Have association_join work with existing model selections

association_join uses eager_graph internally, which uses
graph.  graph requires knowledge of the columns in order
to setup appropriate aliases.

Since association_join just wants the joins and ignores
the changed selection anyway, add a :join_only option to
graph that just does the joins without changing the
selected columns, and have the eager_graph procs use
that option.
Add note about using Model#refresh to get all values in class_table_inheritance plugin

Also add a spec to ensure it doesn't break.
Add documentation note about using symbols for column names on MySQL for certain schema changes

MySQL doesn't have the ability to change the column type, default,
or NULL/NOT NULL setting indepdently, it just has a CHANGE COLUMN
syntax that combines all three settings.  Sequel attempts to parse
the existing values from the schema, but that isn't going to work
unless the column is given as a symbol, since the schema hash is
keyed with a symbol.
Fix error in documentation (two=>to)

Documentation had "two" instead of "to".
Don't associate extension rdoc with Sequel module

RDoc doesn't differentiate file-level RDoc from RDoc for the first
module, so if you only have one RDoc comment block at the top
of the file, and then a class or module after it, the RDoc comment
will be used for both the file itself and the module.

Add empty comment above Sequel module so that the file level
comment isn't used for the Sequel module.
Recognize additional disconnect error in jdbc/jtds adapter