Provide a method-based accessor for SimpleConfig hashes

When SimpleConfig parses a config file that has sections, such as a mysqld
config file, the values within that section are returned via a Hash. However,
we do not provide an easy way to write tests for those deep hash values:

```
describe mysql_conf('/tmp/my.cnf') do
  its('mysqld.expire_logs_days') { should cmp 10 }
end

  MySQL Configuration
     ∅  undefined method `expire_logs_days' for #<Hash:0x007fe463795a00>
```

This change provides a method-based accessor for Hashes that are built via
SimpleConfig.

```
describe mysql_conf('/tmp/my.cnf') do
  its('mysqld.expire_logs_days') { should cmp 10 }
end

  MySQL Configuration
     ✔  mysqld.expire_logs_days should cmp == 10
```

Fixes #1541 by changing the way the attributes are fetched.

Signed-off-by: Adam Leff <adam@leff.co>

lib/utils/simpleconfig.rb

@@ -73,7 +73,13 @@ class SimpleConfig
     m = opts[:group_re].match(line)
     return nil if m.nil?
     @groups.push(m[1])
-    @vals = @params[m[1]] = {}
+
+    # We use a Hashie::Mash to provide method syntax for retrieving
+    # values. For configs that have keys whose values may be hashes
+    # (such as a mysql config that has [sections]), providing
+    # a hash whose values are accessible via methods provide
+    # a better user experience with `its` blocks.
+    @vals = @params[m[1]] = Hashie::Mash.new
   end
 
   def parse_implicit_assignment_line(line, opts)

test/unit/utils/simpleconfig_test.rb

@@ -77,4 +77,11 @@ describe 'SimpleConfig Default Parser' do
     cur.params.must_equal(res)
     cur.groups.must_equal(['g', 'k'])
   end
+
+  it 'provides methods to access returned hashes' do
+    cur = SimpleConfig.new("[section1]\nkey1 = value1\n\n[section2]\nkey2 = value2\n")
+    cur.params['section1'].key1.must_equal('value1')
+    cur.params['section2'].key2.must_equal('value2')
+    cur.params['section2'].missing_key.must_be_nil
+  end
 end