Using correct instance method notation in docs

This matches the Ruby documentation convention of using
`<class>#<method>` to indicate an instance method, vs.
`<class>.<method>` or `<class>::<method>` to indicate a class
method.

lib/wavefile/sampler_info.rb

@@ -11,7 +11,7 @@ class InvalidSamplerInfoError < StandardError; end
   # Public: Provides a way to indicate the data contained in a "smpl" chunk.
   #         That is, information about how the *.wav file could be used by a
   #         sampler, such as the file's MIDI note or loop points. If a *.wav
-  #         file contains a "smpl" chunk, then Reader.sampler_info will
+  #         file contains a "smpl" chunk, then Reader#sampler_info will
   #         return an instance of this object with the relevant info.
   class SamplerInfo
     VALID_32_BIT_INTEGER_RANGE = 0..4_294_967_295    # :nodoc:

lib/wavefile/sampler_loop.rb

@@ -12,7 +12,7 @@ class InvalidSamplerLoopError < StandardError; end
   # Public: Provides a way to indicate the data about sampler loop points
   #         in a file's "smpl" chunk. That is, information about how a sampler
   #         could loop between a sample range while playing this *.wav as a note.
-  #         If a *.wav file contains a "smpl" chunk, then Reader.sampler_info.loops
+  #         If a *.wav file contains a "smpl" chunk, then Reader#sampler_info#loops
   #         will return an array of SamplerLoop objects with the relevant info.
   class SamplerLoop
     VALID_32_BIT_INTEGER_RANGE = 0..4_294_967_295    # :nodoc:

lib/wavefile/smpte_timecode.rb

@@ -6,7 +6,7 @@ module WaveFile
   class InvalidSMPTETimecodeError < StandardError; end
 
   # Public: Represents an SMPTE timecode: https://en.wikipedia.org/wiki/SMPTE_timecode
-  #         If a *.wav file has a "smpl" chunk, then Reader.sampler_info.smpte_offset
+  #         If a *.wav file has a "smpl" chunk, then Reader#sampler_info#smpte_offset
   #         will return an instance of this class.
   class SMPTETimecode
     VALID_8_BIT_UNSIGNED_INTEGER_RANGE = 0..255    # :nodoc: