contactdata 1.1.0

Bug fix

• age_df_countries() now pads single-digit ages with a leading 0 to ensure
  correct ordering. The new behaviour also produces age bin labels that are
  consistent with the labels for the contact matrices

  Before:

      country   age population
  945  France 70_74    3611581
  946  France 65_69    3915473
  947  France 60_64    4123982
  948  France   5_9    4179215
  949  France 55_59    4344144
  950  France 50_54    4445007
  951  France 45_49    4490632
  952  France 40_44    3991502
  953  France 35_39    4097635
  954  France 30_34    4036630
  955  France 25_29    3920126
  956  France 20_24    3959154
  957  France 15_19    4100855
  958  France 10_14    4201067
  959  France   0_4    4070454
  960  France   75+    6352464
  

  After:

      country   age population
  945  France 00_04    4070454
  946  France 05_09    4179215
  947  France 10_14    4201067
  948  France 15_19    4100855
  949  France 20_24    3959154
  950  France 25_29    3920126
  951  France 30_34    4036630
  952  France 35_39    4097635
  953  France 40_44    3991502
  954  France 45_49    4490632
  955  France 50_54    4445007
  956  France 55_59    4344144
  957  France 60_64    4123982
  958  France 65_69    3915473
  959  France 70_74    3611581
  960  France   75+    6352464