Daru::View::Plot can be usable as df.plot(..)

[Shekharrajak]

e.g.

irb(main):001:0> idx = Daru::Index.new ['Year', 'Sales']
=> #<Daru::Index(2): {Year, Sales}>
irb(main):002:0> data_rows = [
irb(main):003:1*           ['2004',  1000],
irb(main):004:1*           ['2005',  1170],
irb(main):005:1*           ['2006',  660],
irb(main):006:1*           ['2007',  1030]
irb(main):007:1> ]
=> [["2004", 1000], ["2005", 1170], ["2006", 660], ["2007", 1030]]
irb(main):008:0> df_sale_exp = Daru::DataFrame.rows(data_rows)
=> #<Daru::DataFrame(4x2)>
         0    1
    0 2004 1000
    1 2005 1170
    2 2006  660
    3 2007 1030
irb(main):009:0> df_sale_exp.vectors = idx
=> #<Daru::Index(2): {Year, Sales}>
irb(main):010:0> df_sale_exp
=> #<Daru::DataFrame(4x2)>
        Year Sales
     0  2004  1000
     1  2005  1170
     2  2006   660
     3  2007  1030
irb(main):011:0> df_sale_exp.plot(adapter: :googlecharts)
=> #<Daru::View::Plot:0x007fa7c1940eb0 @data=#<Daru::DataFrame(4x2)>
        Year Sales
     0  2004  1000
     1  2005  1170
     2  2006   660
     3  2007  1030, @options={}, @adapter=Daru::View::Adapter::GooglechartsAdapter, @chart=#<GoogleVisualr::Interactive::LineChart:0x007fa7c05b2060 @data_table=#<GoogleVisualr::DataTable:0x007fa7c08c2d90 @cols=[{:type=>"string", :label=>"Year"}, {:type=>"number", :label=>"Sales"}], @rows=[[#<GoogleVisualr::DataTable::Cell:0x007fa7c05b3000 @v="2004", @type="string">, #<GoogleVisualr::DataTable::Cell:0x007fa7c05b2f88 @v=1000, @type="number">], [#<GoogleVisualr::DataTable::Cell:0x007fa7c05b2e70 @v="2005", @type="string">, #<GoogleVisualr::DataTable::Cell:0x007fa7c05b2da8 @v=1170, @type="number">], [#<GoogleVisualr::DataTable::Cell:0x007fa7c05b2c40 @v="2006", @type="string">, #<GoogleVisualr::DataTable::Cell:0x007fa7c05b2b78 @v=660, @type="number">], [#<GoogleVisualr::DataTable::Cell:0x007fa7c05b2880 @v="2007", @type="string">, #<GoogleVisualr::DataTable::Cell:0x007fa7c05b2740 @v=1030, @type="number">]], @options={}>, @listeners=[], @version="1.0", @language=nil, @material=false, @options={}>>

[Shekharrajak]

Need some changes for nyaplot but as we know that we are shifting plotting system of daru to daru-view in near future this problem will be solved automatically.

[Shekharrajak]

Anyone can cherry-pick this PR's commit and work on it.