v0.3.5

AccurateArithmetic v0.3.5

Diff since v0.3.4

• Added sum_mixed & dot_mixed: mixed-precision implementations of summation and dot product for 32-bit numbers (#20)
• Fixed four_sum (#18, #21)

Merged pull requests:

• Mixed precision implementations for operations on single-precision inputs (#20) (@ffevotte)
• correct four_sum (#21) (@JeffreySarnoff)