fails to build with GHC 7.8.3 and cabal 1.20

[ababkin]

NOTE: this PR takes care of the build failure. Please merge
#1

Build log:

Configuring aws-sns-0.1...
Building aws-sns-0.1...
Preprocessing library aws-sns-0.1...
[ 1 of 16] Compiling Aws.Sns.Policy.Internal ( src/Aws/Sns/Policy/Internal.hs, dist/dist-sandbox-2352247e/build/Aws/Sns/Policy/Internal.o )

src/Aws/Sns/Policy/Internal.hs:126:24:
Ambiguous occurrence ‘toText’
It could refer to either ‘Aws.General.toText’,
imported from ‘Aws.General’ at src/Aws/Sns/Policy/Internal.hs:73:1-18
or ‘Data.UUID.toText’,
imported from ‘Data.UUID’ at src/Aws/Sns/Policy/Internal.hs:88:1-36
(and originally defined in ‘uuid-types-1.0.2:Data.UUID.Types.Internal’)

src/Aws/Sns/Policy/Internal.hs:130:32:
Ambiguous occurrence ‘fromText’
It could refer to either ‘Aws.General.fromText’,
imported from ‘Aws.General’ at src/Aws/Sns/Policy/Internal.hs:73:1-18
or ‘Data.UUID.fromText’,
imported from ‘Data.UUID’ at src/Aws/Sns/Policy/Internal.hs:88:1-36
(and originally defined in ‘uuid-types-1.0.2:Data.UUID.Types.Internal’)

src/Aws/Sns/Policy/Internal.hs:133:24:
Ambiguous occurrence ‘toText’
It could refer to either ‘Aws.General.toText’,
imported from ‘Aws.General’ at src/Aws/Sns/Policy/Internal.hs:73:1-18
or ‘Data.UUID.toText’,
imported from ‘Data.UUID’ at src/Aws/Sns/Policy/Internal.hs:88:1-36
(and originally defined in ‘uuid-types-1.0.2:Data.UUID.Types.Internal’)

src/Aws/Sns/Policy/Internal.hs:136:61:
Ambiguous occurrence ‘fromText’
It could refer to either ‘Aws.General.fromText’,
imported from ‘Aws.General’ at src/Aws/Sns/Policy/Internal.hs:73:1-18
or ‘Data.UUID.fromText’,
imported from ‘Data.UUID’ at src/Aws/Sns/Policy/Internal.hs:88:1-36
(and originally defined in ‘uuid-types-1.0.2:Data.UUID.Types.Internal’)

src/Aws/Sns/Policy/Internal.hs:596:32:
Ambiguous occurrence ‘fromText’
It could refer to either ‘Aws.General.fromText’,
imported from ‘Aws.General’ at src/Aws/Sns/Policy/Internal.hs:73:1-18
or ‘Data.UUID.fromText’,
imported from ‘Data.UUID’ at src/Aws/Sns/Policy/Internal.hs:88:1-36
(and originally defined in ‘uuid-types-1.0.2:Data.UUID.Types.Internal’)
cabal: Error: some packages failed to install:
aws-sns-0.1 failed during the building phase. The exception was:
ExitFailure 1