Add Base.:+(p::AbstractPolynomial)

[hyrodium]

This PR adds Base.:+(p::AbstractPolynomial) just like +(x::Number) = x in Base.

Before this PR

julia> using Polynomials

julia> q = Polynomial([1,2,3])
Polynomial(1 + 2*x + 3*x^2)

julia> +q
ERROR: MethodError: no method matching +(::Polynomial{Int64, :x})
Closest candidates are:
  +(::P1, ::P2) where {T, X, P1<:Polynomial{T, X}, S, P2<:Polynomial{S, X}} at ~/.julia/dev/Polynomials/src/polynomials/Polynomial.jl:75
  +(::P, ::S) where {T, X, P<:Polynomial{T, X}, S<:Number} at ~/.julia/dev/Polynomials/src/polynomials/Polynomial.jl:58
  +(::P, ::P) where {T, X, P<:AbstractPolynomial{T, X}} at ~/.julia/dev/Polynomials/src/common.jl:864
  ...
Stacktrace:
 [1] top-level scope
   @ REPL[6]:1

julia> a = 3
3

julia> +a
3

After this PR

julia> using Polynomials

julia> q = Polynomial([1,2,3])
Polynomial(1 + 2*x + 3*x^2)

julia> +q
Polynomial(1 + 2*x + 3*x^2)

julia> a = 3
3

julia> +a
3

[codecov]

Codecov Report

Merging #441 (8d26998) into master (419d65e) will decrease coverage by 0.47%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master     #441      +/-   ##
==========================================
- Coverage   82.83%   82.35%   -0.48%     
==========================================
  Files          23       23              
  Lines        2890     2891       +1     
==========================================
- Hits         2394     2381      -13     
- Misses        496      510      +14     

Impacted Files	Coverage Δ
src/common.jl	90.27% <100.00%> (+0.02%)	⬆️
src/polynomials/ngcd.jl	79.66% <0.00%> (-3.90%)	⬇️

Help us with your feedback. Take ten seconds to tell us how you rate us. Have a feature suggestion? Share it here.

[jverzani]

Thanks! I didn't even know unary method existed.