currency: keep amount around in string form for output

Kind of annoying to get things like "1e06 XLM" in the output when we've
been so careful to make sure the converted value won't be printed as
engineering notation. This is a simple fix.

sopel/modules/currency.py

@@ -141,15 +141,15 @@ def exchange(bot, match):
     query = match.string
 
     targets = query.split()
-    amount = targets.pop(0)
+    amount_in = targets.pop(0)
     base = targets.pop(0)
     targets.pop(0)
 
     # TODO: Use this instead after dropping Python 2 support
     # amount, base, _, *targets = query.split()
 
     try:
-        amount = float(amount)
+        amount = float(amount_in)
     except ValueError:
         bot.reply(UNRECOGNIZED_INPUT)
         return
@@ -161,7 +161,7 @@ def exchange(bot, match):
         bot.reply("Zero is zero, no matter what country you're in.")
         return
 
-    out_string = '{} {} is'.format(amount, base.upper())
+    out_string = '{} {} is'.format(amount_in, base.upper())
 
     unsupported_currencies = []
     for target in targets:
@@ -259,10 +259,10 @@ def update_rates(bot):
 
 @plugin.command('cur', 'currency', 'exchange')
 @plugin.example('.cur 100 usd in btc cad eur',
-                r'100\.0 USD is [\d\.]+ BTC, [\d\.]+ CAD, [\d\.]+ EUR',
+                r'100 USD is [\d\.]+ BTC, [\d\.]+ CAD, [\d\.]+ EUR',
                 re=True, online=True, vcr=True)
 @plugin.example('.cur 100 usd in btc cad eur can aux',
-                r'100\.0 USD is [\d\.]+ BTC, [\d\.]+ CAD, [\d\.]+ EUR, \(unsupported: CAN, AUX\)',
+                r'100 USD is [\d\.]+ BTC, [\d\.]+ CAD, [\d\.]+ EUR, \(unsupported: CAN, AUX\)',
                 re=True, online=True, vcr=True)
 @plugin.output_prefix(PLUGIN_OUTPUT_PREFIX)
 def exchange_cmd(bot, trigger):