Fix equation rendering in docstrings (#309)

* fix eqs rendering

* drop {aligned*} environment

* drop {eqnarray*} latex environments

* add aligned envs

* better align

src/functions.jl

@@ -633,10 +633,10 @@ either `Taylor1` or `TaylorN`.
 The coefficients are given by
 
 ```math
-\begin{eqnarray*}
-s_k &=&  \frac{1}{k}\sum_{j=0}^{k-1} (k-j) a_{k-j} c_j ,\\
-c_k &=& -\frac{1}{k}\sum_{j=0}^{k-1} (k-j) a_{k-j} s_j.
-\end{eqnarray*}
+\begin{aligned}
+s_k &=  \frac{1}{k}\sum_{j=0}^{k-1} (k-j) a_{k-j} c_j ,\\
+c_k &= -\frac{1}{k}\sum_{j=0}^{k-1} (k-j) a_{k-j} s_j.
+\end{aligned}
 ```
 
 """ sincos!
@@ -720,10 +720,10 @@ either `Taylor1` or `TaylorN`.
 The coefficients are given by
 
 ```math
-\begin{eqnarray*}
-s_k &=& \frac{1}{k} \sum_{j=0}^{k-1} (k-j) a_{k-j} c_j, \\
-c_k &=& \frac{1}{k} \sum_{j=0}^{k-1} (k-j) a_{k-j} s_j.
-\end{eqnarray*}
+\begin{aligned}
+s_k = \frac{1}{k} \sum_{j=0}^{k-1} (k-j) a_{k-j} c_j, \\
+c_k = \frac{1}{k} \sum_{j=0}^{k-1} (k-j) a_{k-j} s_j.
+\end{aligned}
 ```
 
 """ sinhcosh!

src/power.jl

@@ -177,7 +177,7 @@ exploits `k_0`, the order of the first non-zero coefficient of `a`.
 
     # The first non-zero coefficient of the result; must be integer
     !isinteger(r*l0) && throw(DomainError(a,
-        """The 0th order Taylor1 coefficient must be non-zero
+        """The 0-th order Taylor1 coefficient must be non-zero
         to raise the Taylor1 polynomial to a non-integer exponent."""))
     lnull = trunc(Int, r*l0 )
     kprime = k-lnull
@@ -278,12 +278,12 @@ both `c` and `a` either `Taylor1` or `TaylorN`.
 The coefficients are given by
 
 ```math
-\begin{eqnarray*}
-c_k & = & 2 \sum_{j=0}^{(k-1)/2} a_{k-j} a_j,
-    \text{ if k is odd,} \\
-c_k & = & 2 \sum_{j=0}^{(k-2)/2} a_{k-j} a_j + (a_{k/2})^2,
-    \text{ if k is even. }
-\end{eqnarray*}
+\begin{aligned}
+c_k &= 2 \sum_{j=0}^{(k-1)/2} a_{k-j} a_j,
+    \text{ if $k$ is odd,} \\
+c_k &= 2 \sum_{j=0}^{(k-2)/2} a_{k-j} a_j + (a_{k/2})^2,
+    \text{ if $k$ is even.}
+\end{aligned}
 ```
 
 """ sqr!
@@ -409,12 +409,12 @@ for both`c` and `a` either `Taylor1` or `TaylorN`.
 The coefficients are given by
 
 ```math
-\begin{eqnarray*}
-c_k &=& \frac{1}{2 c_0} \big( a_k - 2 \sum_{j=1}^{(k-1)/2} c_{k-j}c_j\big),
-    \text{ if k is odd,} \\
-c_k &=& \frac{1}{2 c_0} \big( a_k - 2 \sum_{j=1}^{(k-2)/2} c_{k-j}c_j
-    - (c_{k/2})^2\big), \text{ if k is even.}
-\end{eqnarray*}
+\begin{aligned}
+c_k &= \frac{1}{2 c_0} \big( a_k - 2 \sum_{j=1}^{(k-1)/2} c_{k-j}c_j\big),
+    \text{ if $k$ is odd,} \\
+c_k &= \frac{1}{2 c_0} \big( a_k - 2 \sum_{j=1}^{(k-2)/2} c_{k-j}c_j
+    - (c_{k/2})^2\big), \text{ if $k$ is even.}
+\end{aligned}
 ```
 
 For `Taylor1` polynomials, `k0` is the order of the first non-zero